Two days ago, I had oral sex with my girlfriend, who has no stds, and has given my oral sex before with no problems. That night after i went home, suddenly a single red pimple-like lesion appeared on the shaft of my penis. I tried to pop it but im not able to do it. When i tried popping it, some blood and maybe pus came out but not that much, and it also is white on top like a pimple. Is there anyway this is an STD if I had no way to be infected by one? My last sexual contact besides my girlfriend was over a year ago and the lesion only appeared two days ago, and she was clean as well. I want to go to the doctors but i can't for two more weeks until I get my paycheck.