Good question and thanks for asking. He could have what is termed "post-concussive migraine". This can result from mild to moderate head injury
that primes the small branches of the trigeminal nerve
to causes dilatation of the blood vessels within the brain which causes the pounding that classically manifests during a migraine. These migraines are treated in identical fashion to regular migraines. These headaches
he is having may also be cluster headaches, rather than migraines. It's difficult to say without a complete history and physical. Cluster headaches are treated slightly differently than migraines. As for the lymph nodes, their origin could be due to a multitude of factors. It depends on how long these nodes have been swollen. If these nodes are more recent, they are most likely unrelated to head trauma
and possibly due to viral infection, for example. If these nodes became enlarged soon after the head trauma and they have remained that way ever since, it could be due to chronic blockage to lymphatic drainage
and an MRI of the head and neck may reveal the cause. Consulting a neurologist
and ENT specialist
would be helpful in establishing the correct diagnosis and proper treatment. I hope this has helped orient you. Best of luck and health to him!