Answer:
Unless it is your first erection.Go to the doctor
You haven't given enough info..ie, is it iching, is it red ?
I'm guessing it is the penis..Is just the head swollen or all ?
I'd go to the doctor mate.
Ummmm... Charge your male friends to see them?
Probably best to either wait until they go away (they did for me), or go to a doctor and see what he/she says. It's not common, but it's not so unusual.
Unless it's really effecting your life, dont worry about it. It happens with some males during adolecence.