You might want to be careful. I don't want to scare you, but do you have any possible stds, or any possibility of getting any? That's how a lot of them start out. It gets very sore and then more defined. Course if you have an infection it could do the same thing. I would get it checked out.
Even though niceguy was alittle out of his place...He is right. I would take a closer look. Maybe it got rubbed raw after having intercourse, but you want to be careful.
Best wishes!
Carvytaph