Hello, My boyfriend has a huge, greenish bump on his back about the size of a dime, right below his neck that s been there for about a year now. I ve tried popping it with my fingernails but it won t budge and if I do pierce the skin, a HORRIFIC smell comes from the wound. No puss comes out though... it s an extremely hard mass of something. I told him to go get it checked out but he refuses because it doesn t cause him any pain. Is it a boil or a possible cyst? Or perhaps something far worse? Please help. Thank you.