Can someone tell me what this is (pic included)

I had sex with my fiancee last saturday. We've been together for 4 years and this is the first time it happened. When I was peeing the next day it hurts and I thought it might be UTI but I noticed that it stings even when im not peeing. I checked my vagina in front of the mirror and this is what I saw. I have no idea what this is. Please help.

image

that looks like an ulcer which could be herpes , but it may not be. Also herpes can show up at any time and doesnt mean either of you have been cheating or stepping out.

Looks like genital herpes.

Get a blood test done.