congratulations and thank you for breastfeeding! :) it truly is the best! :)
#1: find a local or nearby la leche league leader or group. www.llli.org
#2: make sure that your baby is actually latching on properly (which is probalby something the la leche league leader will ask you or help you with). this means he has to open really wide and you have to make sure he gets your breast in his mouth far enough that you shouldnt have this problem. its hard to do especially if you are in a habit with him of him not getting on far enough. i nursed my son until he was 20 months old (then he self weaned) so i know what its like to nurse a kid with teeth, and i dont remember having any problems. the one time he did try to bite, i just put him down to play and ended the nursing. so thats a tip in case that does happen to you. i only had to do it once, but other kids might need to be reminded over and over, i dont know..
anyway, just try to get more of your nipple area into his mouth. that should help.