Sore, cracked nipples and tender breasts are common problems for new breastfeeding moms.

What causes nursing breasts to hurt? 

Breast engorgement. In those first couple of days after you’ve delivered your baby, your breasts probably won’t be much bigger than they were during pregnancy. Once your regular milk comes in on about the third or fourth day after birth, your breasts will transform and will feel heavy. Breast engorgement (which can be relieved with warm washcloths before nursing, cold packs after, and gentle massage) will last only a few days to a week or so.

What causes sore nipples?

Incorrect latch: 
Latching is crucial for proper breastfeeding, because without a good latch your baby won’t get fed and your breasts won’t be stimulated to produce more milk. Another downside of incorrect latching: all that effort can make your breasts sore, cracked and tender.

If you experience severe breast discomfort and pain — especially if it is accompanied by hardness in the breast, redness, and a fever — you might have a Breastfeeding infection, such as mastitis. Contact your lactation professional immediately. (You should be able to continue to nurse.)