I Have A Large Bump On My Thigh Next To

I have a large bump on my thigh next to my scrotum that has been around a few days. I notice I get these after sex and not showering immediately after (going to bed then showering in the morning) me and my girlfriend are both tested sti free. What is this? Will it go away faster with a certain cream etc? Should I try and pop it? It hurts to touch.