If I were you I would keep pumping on the side with the injured nipple, to keep the milk flowing. Give the pumped milk to baby in a bottle with a nipple resembling human nipples (you can buy these). But make sure that you nurse whenever possible on the side that isn't injured. Maybe rotate feedings like this, one time do the un injured nipple, then the next feed with expressed milk in a bottle, then go back to the nurse again using the nipple that isn't sore and so on...