<s>[INST] Hello, I had a pea sized lump on my collar bone that wasn t painful but movable. suddenly it seemed to scab and surface and looks black...I tried to pop it but it looks like a black ball under the skin and there was no way I could ve. What is this? Should I get it looked at? [/INST] Hi! this is a common clinical problem in the patients visiting my office day-to-day; therefore many people would be happy and benefited to read your post; thanks!I must explain the possibility in this case as follows:lump on collar bone: lipoma, lymph nodes, neurofibroma, hemangioma, cyst, abscess, lymphangioma.painless lump : all possibilities as abovemobile lump: as above except abscessoozing lump: cyst, abscess, lymphangiomalump turned black: recent hemorrhage; therefore a benign cyst only!Only a simple needle biopsy could confirm that this is nothing but a sebaceous cyst; therefore see a surgeon for confirmation and excision which is the best therapy for it!regards, </s>