Thank you for your services.  I am a gay man that suffers from HIV paranoia, but I am also trying to navigate the dating world in a reasonable, safe way.  Yesterday when I was flossing, my hand hit my lip and left a small mark on the outside of it (like the size of a pinhead).  It looked like elevated skin over a small amount of blood, but was not broken.  Several hours later, I had a date and decided to make out with the guy since I know that kissing does not transmit HIV, except during a theoretical possibility where there is obvious trauma and a lot of blood exchanged.  

The date went well, we made out (gently), and I didn't taste any blood.  A few hours later when I got home, the small mark on my lip looked like it had opened.  I wasn't obviously bleeding since it was so small, but there was a miniscule amount of blood when I rubbed toilet paper on it.  I obviously don't know when it opened (entirely possible that I did that with the toilet paper), but you can figure out my concern.  

I should note my date is on PrEP, and I believe you have to be HIV negative to continue on the medication but I'm not sure and don't want to ask because I'll come across as overly anxious and he might take my anxiety the wrong way.  

I guess I'm looking for reassurance.  I'm also wondering if it safe to make out in general when my mouth is not in perfect condition, like a day-old, self-inflected bite on the inside of my mouth, etc.  

I'll be glad to comment.  There are no data to suggest that HIV is ever transmitted by kissing of any sort.  This is true even with the presence of theoretical factors which might enhance transmission such as lip sores or cuts, dental or gum disease or cuts or abrasions on the lips, tongue or mouth. Your risk, IF he was HIV infected (most unlikely) is theoretical in the same sense that theoretically you could be struck by a meteorite falling from space while reading my reply, i.e.  it is just not something to worry about.  I see no reason for concern and no need for testing related to the encounter you have described.

I hope that this information is helpful.  EWH