What could this be?

so doctor has pcr swabbed and came back negative for herpes. it did itch and blister up. single sore. but if not herpes, the what the heck could this be!? showed up ~5 days after sex

at this point i just want to know what could cause a sore like that if not herpes. neither doctor ive seen could give me an answer

Its body reaction due to infection in the body that wasnt treated well. It will go away gradually but just be patient. You can apply something but i dont know if you will like to.

what could i apply? doc gave me antibacterial cream