Please help I'm getting very stressed

I'm breastfeeding my son and he bit my nipple but I never felt him doing it. It just appeared all cut and it's taken ages to heal because I keep feeding him and it gets worser and is no bleeding. What do I do. I alos have Mastitis in the same breast with the cut so this is all really annoying me. I cant feed my boy as it's bleeding because of the blood, should I buy nipple shields, I really dont know