I had this sore on my breast that was dark purple/black and about the size of a quarter or bigger. It was raised (like a cyst) and protruded outward through the skin. It was really itchy and very, very sore if my breast moved at all due to walking, running, etc. Well a couple days after noticing it, it "popped". It reduced in size dramatically but there is an open area about the size of two pinholes put together. There is some pus that comes out, very minimal. What should I do about this?