finger play and stis?

Sarah
So my on and off boyfriend of 2 and a half years and I were just doing hand stuff and ever since (about 3days) my vagina has been swollen and red on one side and there's this weird blister type thing, it's only tiny(about the size of a pea) and I zoomed for obvious reasons
I know online sources aren't very reliable but they all said its next to near impossible to transfer stis from hand play 
Could this be a cut healing or perhaps friction burn? If it's not better in the next few days I'll consider going to the gyno