Brief Answer:
Needs management and some workup

Detailed Answer:
Thank you for asking
Your kid's sudden headaches of such severity are worth assessment and needs a cranial work up like CT MRI Lumbar puncture to rule out any suspicion of some morbid trouble like infection , abscess or tumor etc to be on the safe road.
Once cleared then No worries it will be just a migraine and that will need diet and lifestyle modifications.
Headaches in children are common and usually aren't serious. Like adults, children can develop different types of headaches, including migraine or stress-related (tension) headaches. Children can also have chronic daily headaches.

In some cases, headaches in children are caused by an infection, high levels of stress or anxiety, or minor head trauma. It's important to pay attention to your child's headache symptoms and consult a doctor if the headache worsens or occurs frequently. Headaches in children usually can be treated with over-the-counter pain medications and other lifestyle measures.

A number of factors can cause your child to develop headache. Factors include:

Illness and infection. Common illnesses such as colds, flu, and ear and sinus infections are some of the most frequent causes of headache in children. More-serious infections, such as meningitis or encephalitis, also can cause headache, but are usually accompanied by other signs and symptoms, such as fever and neck stiffness.
Head trauma. Bumps and bruises can cause headaches. Although most head injuries are minor, seek prompt medical attention if your child falls hard on his or her head or gets hit hard in the head. Also, contact a doctor if your child's head pain steadily worsens after a head injury.
Emotional factors. Stress and anxiety — perhaps triggered by problems with peers, teachers or parents — can play a role in children's headaches. Children with depression may complain of headaches, particularly if they have trouble recognizing feelings of sadness and loneliness.
Genetic predisposition. Headaches, particularly migraines, tend to run in families.
Certain foods and beverages. Nitrates — a food preservative found in cured meats, such as bacon, bologna and hot dogs — can trigger headaches, as can the food additive MSG. Also, too much caffeine — contained in soda, chocolates, coffees and teas — can cause headaches.
Problems in the brain. Rarely, a brain tumor or abscess or bleeding in the brain can press on areas of the brain, causing a chronic, worsening headache. Typically in these cases, however, there are other symptoms, such as visual problems, dizziness and lack of coordination.

OTC pain medications, such as acetaminophen (Tylenol, others) and ibuprofen (Advil, Motrin IB, others), are usually effective in reducing headache pain. Before giving your child pain medication, keep these points in mind:

Read labels carefully and use only the dosages recommended for your child.
Don't give doses more frequently than recommended.
Don't give your child OTC pain medication more than two or three days a week. Daily use can trigger a rebound headache, a type of headache caused by overuse of pain medications.
Use caution when giving aspirin to children or teenagers. Though aspirin is approved for use in children older than age 2, children and teenagers recovering from chickenpox or flu-like symptoms should never take aspirin. This is because aspirin has been linked to Reye's syndrome, a rare but potentially life-threatening condition, in such children. Talk to your doctor if you have concerns.
In addition to OTC pain medications, the following can help ease your child's headache:

Rest and relaxation. Encourage your child to rest in a dark, quiet room. Sleeping often resolves headaches in children.
Use a cool, wet compress. While your child rests, place a cool, wet cloth on his or her forehead.
Offer a healthy snack. If your child hasn't eaten in a while, offer a piece of fruit, whole-wheat crackers or low-fat cheese. Not eating can make headaches worse.

The following may help you prevent headaches or reduce the severity of headaches in children:

Practice healthy behaviors. Behaviors that promote general good health also may help prevent headaches for your child. These lifestyle measures include getting plenty of sleep, staying physically active, eating healthy meals and snacks, and avoiding caffeine. There's some evidence that being overweight, smoking and getting little physical activity contribute to headaches in adolescents.
Reduce stress. Stress and busy schedules may increase the frequency of headaches. Be alert for things that may cause stress in your child's life, such as difficulty doing schoolwork or strained relationships with peers. If your child's headaches are linked to anxiety or depression, consider talking to a counselor.
Keep a headache diary. A diary can help you determine what causes your child's headaches. Note when the headaches start, how long they last and what, if anything, provides relief. Record your child's response to taking any headache medication. Over time, the items you note in the headache diary should help you understand your child's symptoms so that you can take specific preventive measures.
Avoid headache triggers. Avoid any food or drinks, such as those containing caffeine, that seem to trigger headaches. Your headache diary can help you determine what prompts your child's headaches, so you know what to avoid.
Follow your doctor's plan. Your doctor may recommend preventive medication if the headaches are severe, occur daily and interfere with your child's normal lifestyle. Certain medications taken at regular intervals — such as certain antidepressants or anti-seizure medications — may reduce the frequency and severity of headaches.

Usually you can treat your child's headache at home with rest, decreased noise, plenty of fluids, balanced meals and over-the-counter (OTC) pain relievers. If your child is older and has frequent headaches, learning to relax and manage stress through different forms of therapy may help, as well.

Medications

OTC pain relievers. Acetaminophen (Tylenol, others) or ibuprofen (Advil, Motrin IB, others) can typically relieve headaches for your child. They should be taken at the first sign of headache.

Use caution when giving aspirin to children or teenagers. Though aspirin is approved for use in children older than age 2, children and teenagers recovering from chickenpox or flu-like symptoms should never take aspirin. Aspirin has been linked to Reye's syndrome, a rare but potentially life-threatening condition, in such children. Talk to your doctor if you have concerns.

Prescription medications. Triptans, prescription drugs used to treat migraines, are effective and can be used safely in children older than 6 years of age.

If your child experiences nausea and vomiting with migraines, your doctor may prescribe an anti-nausea drug. The medication strategy differs from child to child, however. Ask your doctor or pharmacist about nausea relief.

Caution: Overuse of medications is itself a contributing factor to headache (rebound headache). Over time, painkillers and other medications may lose their effectiveness. In addition, all medications have side effects. If your child takes medications regularly, including products you buy over-the-counter, discuss the risks and benefits with your doctor.

Therapies

While stress doesn't appear to cause headaches, it can act as a trigger for headache or make headache worse. Depression and other mental health disorders also can play a role. For these situations, your doctor may recommend one or more behavior therapies, such as:

Relaxation training. Relaxation techniques include deep breathing, yoga, meditation and progressive muscle relaxation, which is accomplished by tensing one muscle at a time, and then completely releasing the tension, until every muscle in the body is relaxed. An older child can learn relaxation techniques in classes or at home using books or tapes.
Biofeedback training. Biofeedback teaches your child to control certain body responses that help reduce pain. During a biofeedback session, your child is connected to devices that monitor and give feedback on body functions, such as muscle tension, heart rate and blood pressure. Your child then learns how to reduce muscle tension and slow his or her heart rate and breathing. The goal of biofeedback is to help your child enter a relaxed state to better cope with pain.
Cognitive behavioral therapy. This therapy can help your child learn to manage stress and reduce the frequency and severity of headaches. During this type of talk therapy, a counselor helps your child learn ways to view and cope with life events more positively.

I hope it helps. Take good care of yourself and your child and dont forget to close the discussion please.
May the odds be ever in your favour.
Regards
Khan

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