Oral Sex - Help!

I gave my first blowjob to my boyfriend of 5 months on News Year's and I noticed I have a bump in my mouth? It's a single bump, looks like a miniature pimple with redness and it's hurts but only when touched, it is on the inside of my bottom lip. I know both of us are STD free, I didn't make him use a condom and he did ejaculate into my mouth. What else could it be, and should I be worried?