The blistering and opening makes me think that it is herpes. Your body can react in weird ways to different things, but I'm not sure what else causes open sores (I'm sure there are things).
Still, you probably have more experience with the "signs" that something is herpes or isn't.
Also, the sex is most likely a coincidence.
If you have had "cold sores at the exact same spot" youve probobly have had herpes all along. This could be a larger outbreak due to something with your immune system, or maybe its something else.
Since this bothers you I think you should see a doctor.
I went to the dermatologist that next day. She scraped the area and looked at it under a microscope. She said it was an infection caused by yeast but it brought on in times of stress and sleep deprivation. I asked her if it was contagious and she said obviously the spores of the yeast infection IF transferred to an open sore could be.
The downside to this was the gel to treat it was REALLY pricey and was not covered by insurance but the dermatologist gave me a $25 card from the mfg. so that I could still get the prescription. Now that it's starting to heal it itches insanely and is NOT cute.
I asked her if it was related to herpes and she said no because it was symmetrical from one side of my face to the other. She said herpes outbreaks do not cross the center lines of the face (this was news to me).
The gels and stuff for dermatology stuff can be pricey. One tube of cream I needed for my fungal infection was 200.00. I was shocked.