While showering, I discovered a nickle size lump, with what feels like a blister on the crack of my butt. It's not close enough to the anus, to think it's a possible hemorrhoid. What I thought was a blister, looks more like a mole, because it's darker than a regular looking blister. The stream of the shower was painful. What could this be? Should I see a doctor? It may have drained just a bit. I've never experienced this before. Thank you.