I am an 18 and have a steady girlfriend. we have protected sex but a couple days ago i noticed a pimple, abou 2-3mm, on the base of my shaft near my pubic hair. we haven't had sex in about a week (that time of the month for her) but i noticed it popped up. i haven't popped it because i know that could make it worse, i'm just wondering if it's just a pimple or possibly an sti. i had an injury to my head a few days ago and by doctors orders i have to keep the area dry, which unfortunatley means i hadn't been able to shower for a few days (i know, gross but doctors orders.) in the last couple of days, i've washed it with anti-bacterial wash. is it just a pimple or could it be more? any help would be great.

thanks