A nipple shield is usually used with newborns to protect a mom’s nipple when the infant is first learning to breastfeed. By now your baby is so used to the feel of your nipple that it would probably be very hard if not impossible for him to transition to a nipple shield now. Also nipple shields may decrease your milk production since they do not allow for all of your milk ducts to be properly drained, which will just make your little guy even more frustrated (and also cause you to become very sore and putting you at risk of developing mastitis!) I would recommend paying very close attention to your baby during a breastfeeding session and take him off the breast as soon as he is finished sucking. If he does bite, I would pull his face towards your breast, forcing him to let go, then end the nursing session right away. Try not to get angry and scold him as some babies find this funny and may just make the problem worse!