After My Girlfriend Rubbed On My Penis I Noticed It

After my girlfriend rubbed on my penis I noticed it stung near the head. Upon further inspection I noticed a slight scratch that was barely visible. Well later we had sex and I noticed the scratch got bigger (almost looks like a tooth bite) and I had a pimple with a white head that I squeezed the pus out of and it went down but hasn't gone away and ive had both of these problems nearly a week. The bump doesn't hurt at all but the scratch stings when water hits it at first what should I do?