It won't cause a problem over a day or so, giving your sore nipple time to heal. Expose your nipples to air between feedings so they heal faster. You can also help them heal faster by squeezing some breast milk onto your nipples, rubbing it in gently, and allowing it to air dry. Open the flaps of your nursing bra and wear a loose cotton blouse or t-shirt. Exposing your breasts to sunlight for 10 to 15 minutes at a time can help too.
Some women even dry their breasts briefly with a hand-held dryer on a low setting.
Talk with a nurse, lactation consultant, or other health care professional who works with breastfeeding mothers. She'll be able to help you and your baby with nursing. A small amount of modified lanolin may help heal your sore nipples. Before applying it to your nipples, you should use a little on your arm and check it 24 hours later for redness or other signs of allergy. As a last resort, if you feel like you have to stop nursing for even one day, pump your milk every three hours.