There's a bone protruding from the back of his head. What's going on?

There is a raised bone in the back of the head. There are many reasons. It is also a more common symptom. It is normal. External occipital tuberosity, don't worry too much, don't massage, if there is no pain, you don't need special treatment. If you show pain symptoms, it may be caused by hyperosteogeny. If the symptoms are mild, surgery is not needed. Physical therapy can be chosen to alleviate the condition. It is best to do a detailed and careful examination, do a ct, may also be caused by congenital bone dysplasia, usually pay more attention to physical exercise, regular physical examination.