Do not let your baby take only the tip of your nipple. Make sure the baby gets enough of the lower part of the areola in her mouth. Not doing so is a common cause of sore nipples. During the feeding hold your breast from below so the nipple and areola aren't pulled out of your baby's mouth by the weight of the breast. Begin a feeding on the less sore nipple to trigger your let-down reflex and start milk flowing.
Babies suck harder at the beginning of feedings.
After your baby has nursed briefly and milk flow has begun, move her to the second breast. This should make nursing more comfortable because the baby will suck less vigorously once milk starts to flow. However, as soon as possible, resume switching the breast you start each feeding with to prevent a lopsided milk supply. Frequent shorter feedings are preferable to less frequent lengthy feedings. If one nipple is extremely sore, temporarily limit feedings to 10 minutes on that side.