I am freaking out here. So earlier this week (starting Monday) I was experiencing streplike symptoms (fever, white patches on throat; exactly how strep starts for me) and I also started my period on Tuesday. About two days ago I noticed a little dryness/itchiness when I wipe down there and yesterday it turned painful. So I took a look and it looks like a penny-sized white/pus canker sore (not cold sore) ulcer-like thing is on the inside of my inner labia. My labia is also a bit swollen. The ulcer is painful when I touch it or try to urinate (because the urine touches it) but doesn't bother me otherwise. I have no idea what this is. I'm only 20 years old and have never had sexual intercourse or oral sex and haven't kissed anyone in months so it can't be an STD (and it doesn't look like herpes). Also my strep symptoms have mostly gone away (no fever, no more white patches, just a little redness on one side) and I didn't go to the doctor because I've been busy/stressed with college exams this week. But what the heck could this ulcer thing be?

There are many possibilities. It could be an ingrown hair, it could be a pimple, a cyst, a tumor, and many other things.

There's really no way to diagnose it online. You will have to make the time to see your doctor.