Rinse it under near-scalding hot water then have someone take you to a hospital to make sure a piece of the stinger isn't inside the wound. Necrosis is a main concern, which is why a trip to the hospital is mandatory. You'll want to go anyway, as the pain is severe.
no no.. im pretty sure you never want to cut a stinger.. pretty sure it can hurt or even kill a ray. you dont really have to worry about it hurting anything.. just dont piss it off. and you will be fine just wait till you can hand feed it