Some mothers have sore nipples, even if their babies seem (to an untrained eye) to be properly latched on. Pain always indicates a problem that needs to be diagnosed and resolved. Ask the pediatrician and/or your lactation consultant to examine your baby's mouth. She may have a high palate, or a short or tight frenulum (the tissue under the tongue) that makes it difficult for her to use her tongue.

Causes of sore Nipples:

• If breastfeeding already is established, and your nipples are suddenly sore, you may have thrush. To properly diagnose thrush, both you and the baby should be examined by a lactation consultant and then by your physician.
• If your nipples are red and sore, but thrush has been ruled out, another possibility is eczema of the nipples. This occurs in women with a history of eczema and dry, sensitive skin, and it usually is accompanied by burning and itching.
• Sore, tender nipples also can signal pregnancy, especially if you're also exceptionally tired and nauseated.
• you could have a breast inflammation or infection.
• you could have a bacterial infection in your nipples.
• If you've eliminated infections, inflammation, thrush, and positioning as the culprits, you should see a dermatologist familiar with breastfeeding-related problems.
• It may also be due to breast pump trauma.
• Nipple blister may also lead to nipple soreness.
• Milk bleb. A milk bleb is caused when a thin layer of skin grows over a milk duct opening, causing milk to get trapped and clog up the duct. The bleb tends to look like a white or yellow dot on the nipple and may cause pinpointed pain at that spot and just behind it. 

Tips for preventing or healing sore nipples:

• Check the baby's position when she latches on. Make sure the nipple is pointing at the back of her mouth and that she's encompassing as much of the nipple and areola in her mouth as possible.
• Make sure the baby's lower lip is flanged, not sucked into her mouth. Pull down his lower lip. You should be able to see his tongue between his lower lip and your nipple.
• Use warm compresses and expressing a little milk to soften nipples hardened by engorgement.
• Use your finger to break the baby's latch suction, rather than pulling the baby off your breast