Good news: I don't think you're alone.
Meh news: If it falls in line with what I've been looking into, there aren't a lot of immediate answers as to what it is, why it's there, how it's treated or what happens if not.
I experienced similar irritation a few days after unprotected oral sex, and about two months later it hasn't really subsided. In the meantime, I might suggest mixing 1 part tea tree oil and 3 parts olive oil and applying in with a q-tip or cotton ball twice daily to the affected area (and then some). I can't promise it will go away, but it seems to offer a little relief in some cases. Staying hydrated and drinking acidic juices also seems to help with any urinary discomfort, again- uncertain if these are related. Be sure to get and STI screening when you can, to rule out any other culprits.
Take care of yourself in the mean time and try to relax as much as possible. It may not go away, but it shouldn't cloud your life.