Have A Little Bump Under Skin That's Been There 8-10

Have a little bump under skin that's been there 8-10 years. It's under a very small (smaller than tip of eraser) little pitted area that has what looks like a tiny black head or very dark spot inside. It recently flared up and became tender, red & warm. (I had been checking self for skin changes and wanted to see if that had grown underneath.) Anyway, after becoming tender, I pressed it and cheesy, green substance came out followed by bloody watery discharge. Thoughts?