hey buddy... i've had this happen before. it's always been after a hard sex session and the guy i've been with hasn't been too careful when giving me head. there are also other things that have caused it that I won't go into here, but it usually clears within the week.
my bf's nephew says he got one cuz his girl sucked too much on it. went to std clininc and they told him it was broken blood vessel but they didnt tell him how to get rid of it. he asked us and we told him maybe a dermatologist or urologist? does anyone know? its so funny lol. we give him hell.