Inflamed/bump on tip of penis

Patient: Hi,About 5 weeks ago I had a sexual encounter with a man. This was my first time ever doing something with a man. We masturbated with each other and I briefly licked the shaft of his penis and scrotum. I had my hand placed on the head of his penis to make sure not to make contact with it. I have recently noticed a slight bump/inflamed on the very tip of my penis, the urethra. Could I have possibly contracted some kind of std or could this be something else. I am not sure if this makes helps but I do masturbate often and use a sock or my underwear to wrap around my penis to catch the ejaculation. I am extremely worried that this encounter might have infected me with something but I am also wondering if that encounter is just really worrying me and I am over reacting. Your help is greatly appreciated.

Symptoms: Inflamed/bump on the tip of penis (urethra)