HI,Welcome to HCM. Based on the facts of your query,Your son seem to have Chronic SOL with old head injury.The consistent pain with headache and dizzy feeling,needs one to rule out the Chronic SOL./ or could be due to infected hematoma with calcification of the resolving hematoma-this is what is calcium build up. A simple antibiotic /painkiller treat would help your son.If no relief, get CT skull and USG,if infected hematoma-Simple Wide bore Needle Aspiration would help to relieve this son. But as dizzinees is associated possibility of Chr SOL needs to be ruled and if found would need Burrhole decompression for the Cerebral Compression with Intracranial hypertension associated with Chronic SOL(Space Occupying Lesion) of the skull. Hence I would suggest to - Get Second opinion from Surgeon,who would physically check and if need be get USG done to find out the cause of this swelling near back of head.This would give you the best lead to treat it by medicines or by surgical intervention as suggested from expert-Surgeon. CT Skull would resolve the issue of ambiguity in causes of this knot at the base of the skull. Hope this reply would help you to know what you should do? in your case,in the best possible way. Welcome for any further query in this regard Will appreciate writing your feedback review comments,to help the needy patients like you at HCM. Good Day!! Dr.Savaskar, Senior Surgical Specialist M.S.Genl-CVTS