Does this sound like a STD?

Basically, I had a one night stand, used a condom but it broke midway. 2 months later I noticed this rash on my penis on the shaft. The rash looks like a group of little bumps, but when u run ur hand over it, it’s As smooth as my other clear shaft skin. They’ve been here 9 days and haven’t grown or shrank at all. They don’t hurt or itch nor do I have any other side effects. I do wear tight underwear daily (ethikas) and I saw that it can cause pimples and other bumps down there but I’ve been wearing those for about 4 years and never seen nothing like this. I plan to get tested this weekend, just wanna see if anyone has ever had something similar or knows what it might be. Can’t find anything on google that matches what I have. Just wanna know what I’m walking into on test day.