Please don't tap your baby on the face as reprimand. No one likes to be scolded that way... just my two cents...
Good advice at this site:
When baby bites:
http://www.kellymom.com/bf/older-baby/biting.html<snip>
If baby bites, it can be very effective to calmly remove baby from the breast and say nothing (or perhaps make a calm comment like "oh? don't want to nurse right now?"), then end the nursing session for a bit.
Stopping the nursing session is generally the most effective way to teach baby that nursing and biting do not go together. Once baby lets go, remove her from the breast for a bit - it may be a few seconds or a few minutes (this is something where you'll need to gauge your own baby's reaction). If baby is teething (which is often the cause of biting), this is a good time to hand baby something cold to chew on, a teething toy, etc. You might tell baby something along the lines of, "if you want to bite, we're not nursing." If baby really wants to keep nursing, she may get upset when you end the nursing session, at which point you can wait a few moments then give baby another chance to nurse. If baby is not interested in nursing, she might fuss a few seconds but then go on to something else.
If baby bites,
it's not a good idea to scream or yell on purpose as a method to stop biting -- there are better ways to teach baby not to bite. Sometimes, of course, it's impossible not to yell in pain if baby catches you by surprise and/or bites hard. Sometimes yelling does stop baby from biting again; however, some babies think it's so funny that they continue to bite for the reaction, and other babies are so scared that they go on a nursing strike. The chance that this method will stop baby biting is simply not worth the problems it can cause.
If your baby bites down and doesn't let go (most let go immediately without mom doing anything), there are a couple of things you can do: First, quickly place your finger between baby's gums so you can pull away without (more) injury. If that doesn't work, pull baby TOWARD you, very close to your breast. This will make it a little hard to breathe, so baby will automatically let go to open her mouth more and uncover her nose to breathe. A variation of this that some moms use is to gently pinch baby's nose closed for just a second to get her to open her mouth and release the nipple.
From other moms:
<snip>
"A baby cannot suck for milk and bite simultaneously. When I start to nurse my son, I watch him intently. As soon as he stops sucking, I take him off the breast and talk to him gently for a minute before I let him resume."
"What worked best for me was to be very vigilant during nursing sessions - no more reading magazines or watching TV. By watching carefully, I could tell when my son was beginning to lose interest, and I could remove him from the breast."
"Be sure you don't use any teething gels or lotions just prior to breastfeeding, since it can numb the baby's tongue, and even your nipple & areola, making it difficult for baby to breastfeed."