Met creepy guy sucked and bit my bottom lip hard. Fat lip now. Who do I tell?

Stay away from creep. Suction may have produced swelling. Can apply ice to help swelling go down.
Doctor, Plastic surge. Go to ypur plastic surgeo if he is available immediately, or go to emergency room. More than likely, swelling will go down in time, but you need prophylactic treatment to prevent infection and tetanus.