<s>[INST] Ive had a pea sized hard bump under my skin at the base of my skull for about 10 years.  Its never hurt, moves around, Ive had 2 doctors check it out. They are not worried about it.  Last night I touched it with my finger and it seemed to have a scab on it.  Had my daughter look at it, she said it was a light colored scab. As I touched it with my finger it shot out puss.  Since then Ive seen white & dark puss, nasty smelly stuff.  It definitely was bigger than its ever been but was flat by the time I went to bed (vecause I sqoze everything out).  This morning its not too big but still has smelly nasty stuff coming out. Help!  Should I call my doctor or is it likely to go away on its own? [/INST] Welcome to Chat Doctor .1. Its infective collection, probably previously it was a lipoma and in got infected recently causing collection and pain.2. In this case treatment is to get an antibiotic course, but if it is complicated and big - it may need a small incision and Chat Doctor. 3. Do not scratch, press or irritate the lesion - it will only get complicated and delay in healing process.4. Clean area with antes epic liquids and avoid touching that will heal soon.5. Yes you need medical help, call up and make an appointment and get the needful things done. Good luck. Hope it helps you. Wish you a good health. Anything to ask ? Do not hesitate. Thank you. </s>