Red bump on head of penis

Patient: I have a red bump on the head of my penis. It just appreared yesterday and seems to not go away. Ive had bumps and rashes from rough sex or too much masturbation, but this seems different. It is a red bump slightly raised, looks almost like a pimple.The reason for concern, is that I was recently bit in a fight and am worried I might have contracted an std or something else.

Symptoms: No symptoms besides the visible area.

Doctor: