Could be an STD, maybe gonnoreah, or chlamydia? If not maybe a UTI, or even a blockage of the urethra. Don't have intercourse and go to the doc to get checked out. If it is an STD and you have intercourse and spread it to someone else, and then go and get treated and cured, and then have sex with her again you will just get it back again, so go ASAP to the DOC!!!
Without knowing anything else, that sounds like a classic case of syphilis or gonorrhea, both of which will need a visit to the doctor to make sure it doesn't progress past the first stage.Why does my tongue hurt?