male, 22, 5 3, 160 pounds. no prior health problems. there is a sore that looks like a bubble about the size of a pea, perfectly round, that is on the upper right butt cheek by the crack. it has a red dot on top. originally thought it was a zit, squeezed, and blood came out. no puss. it doesn t bleed anymore, but is painful if touched, and hasn t gone away. been there for about 3 months now. what is it?