About A Month Ago I Noticed A Hive-like Itchy Bump

about a month ago I noticed a hive-like itchy bump on the back of my middle finger. I kept messing with it and it got worse, filled with puss, and after I popped and drained it it seemed to go away. now I have a large, raised (yet barely visible) hard welt there that itches like crazy and the skin over and around it is always flaking and peeling. it's not a blister, it kind of looks like scar tissue. a friend of mine says it may be associated with methamphetamine use. what is it and how do I make it go away?