3 small cuts between vag and butt?

these cane out of nowhere and it stings when i pee, i was fine yesterday. i haven't had sex in about 2-3months, and my period just ended yesterday. i did go to the gym for the first time in about a year but that the only thing I did out of the ordinary. I did mostly leg workouts.

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could this be an STD?

My girlfriend had this once. It turned out to have been from her doing yoga.