Thats what I'm thinking. It actually popped after taking a shower and a little puss and blood came out just like a pimple. It's the only one and its flat now with a tiny scab. I think Im just freaking out I'll give it a few days to heal and see what happens.
Optical, that looks very similar to a pimple caused from an ingrown hair. If this is an isolated incident I wouldn't worry about it. Get checked out of it will make you feel better.
To look at the picture so you see for sure what I am talking about http://tinypic.com/r/rab7z8/5 It is the only one on my penis and I have had unprotected sex before.