If it's a lump of reddish/bloody skin, probably a hemmie. Could also be developing an abscess. Doing the "nasty" back there could cause tearing as well, this in-turn allows all the nasty bacteria to get into the tear and cause infection. If it gets too painful, go to doc/ER and get it checked out. I went to ER with a perianal abscess a couple of months ago. I probably let it go too long because I was embarrassed a bit. Everyone treated me with respect. This is not as uncommon as one might expect. It's just no one ever talks about it. Not many people I know, know about the extra hole I got next to the one God gave me. Oh yeah, and that it leaks poopy juice constantly. If it bothers you too much, get your arse to the doc and get something to help with the pain.