If your baby is chewing down on your nipple when nursing, perhaps it’s time to let her chew on something else. Take a clean cloth and submerge it in water. Wring it until it is damp, and then place it in the fridge. Once it’s cold, you can give it to your baby to chew on to help mitigate their aching gums.
Before nursing, try giving your baby a finger. If they suck, they are not in discomfort, and can nurse fine. If they bite down, perhaps you should give them something to chew on before they nurse on your breast.