What is the mystery scab on penis shaft base?

[Godofspidsrs]

I haven't been sexually active for 2 months.  Never had a problem like this before.
New girlfriend and I were having a very heavy petting session yesterday and today I saw a very red scab or blister of some sort on the base of the shaft of my penis. Looks like a blood blister or scab, possibly a cut as well beneath but it isn't painful and it's relatively soft to the touch. Yesterday I was fine.
I saw it and kind of freaked out. Could it be an std of some sort? Could my gf have friction burned the base and given me a sore of some sort. If I pull the skin around it it's a bit sore, but otherwise I had no idea it was there. I'm terrified of the idea of having an std but I want to get an opinion before i rush to the doctors or tell girlfriend about it

[Life360_Dave]

Hi since it happened right after the petting it would appear as a friction burn as no std shows symptoms the next day.

[Godofspidsrs]

Thank you. Sorry it just kind of freaked me out