The cut could have happened during intercourse, if you're sexually active. You may want to get in to see your gynecologist to find out what's going on.
Hello,
This cut could be a fissure, fistula or urethral caruncle which is a benign granulomatous lesion of the distal urethra. So get an evaluation done from a gynecologist as if it is a urethral caruncle then you may need to consult a urologist to confirm the diagnosis.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.