Welcome to the forum. It is time for you to get your son in an emergency room. Consult a doctor an d let your son get clinically assessed. He needs to be physically examined, especially his abdomen and genital area ( scrotal sac, testicles, penis ). Since he is 11 years of age, the most common suspect will be Orchitis
or epididimo-orchitis. Orchitis is a condition when the testicles get inflamed with or without the inflammation of the epididymitis
. It causes pain, fever
, patient gets nauseous or dizzy. ( it is often due to viral mumps
infection). Your son needs medications and anti-inflammatory drugs to help him with the symptoms.
Though you have not mentioned, if the symptoms are after a blow or injury
to the scrotal sac, it can be due to testicular tortion ( a medical emergency). The other differential diagnosis can be inguinal hernia
due to weakness of the muscle ( medical emergency ) or tortion of the testicular appendage ( common in children) or kidney
stone ( rare chance in this case). You need to get investigations ( blood tests, analysis of urine ( routine/ culture sensitivity) to rule out infections.
Your son will get fine but may need antibiotics, anti-inflammatory drugs, scrotal support, icepacks, etc depending on the severity of the symptoms and diagnosis. Get him checked up. Have a good day, take care.