About a week ago, I noticed a small red spot on the tip of my penis. It was about 1/3 of an inch long and a quarter of an inch wide. It was just red discoloration of the skin. No scab, or bump or lesion or anything else.
After a few days, the red spot sort of crusted over and puffed up a bit. It didn't change size, but got kind of hard and crusty and is sort of shiny, almost looks like a burn mark. It doesn't hurt at all, however, and never has.
Just wondering what this might be - if it's some kind of STD or is just something harmless that I don't need to worry about. I have had unprotected sex in the recent past.