<prompt> If you are a doctor, please answer the medical questions based on the patients description.I have noticed a large bone like lump on the back left hand side of my skull just above the base of skull it was not there earlier and have not bumped or banged it. It is not painful to touch and I have no headache at the moment but I do suffer from severe headaches and migraines sometes for days at a time.  <response>: Hi, I read carefully your question and would explain that there are different causes that may lead to these symptoms: a bone tumor, vitamin D deficiency, an intracranial lesion like meningioma. Coming to this point, I would recommend consulting with a neurologist for a physical check up and some tests: - a brain CT scan-blood electrolytes- PCR, sedimentation rate for inflammation. If all these tests result normal, there is nothing to worry about Hope I have answered your query. Let me know if I can assist you further. Kind regards, 