My ex-boyfriend actually had that issue and we were concerned. It turns out it was a boil, and can be pretty common. It was NOT an STD, though I do not know if this is the case with you. In my ex's case, the boil is an infection and can be treated with antibiotics. So check to see if you have a temperature. If you choose not to go, do not touch the infected area unless you do compresses with a warm wash cloth. In intervals of twenty minutes you should be able to get the puss to form a head like you get with a zit. Be gentle with it or it can get Much worse. If it continues to get red and grow call the doctor! Good luck!