I'm wondering what a cold sore feels like when it is coming? As well as, how does it feel when it is there?

A couple weeks ago, I had a STD scare. I'm clean (I think). I got tested when I got the scare and everything came back normal. I did have a face rash called perioral dermatitis. It does itch every now and thing. Not harmful just annoying.

I have very small bumps near my lip, I believe it is the perioral dermatitis because they don't hurt or burn. No tingling. Nothing. I go to the doctor Thrusday, but I would like some advice from someone that does get cold sores if they don't mind.