I have worked with a few women who have had persistant cracked nipples.
They have successfully and quickly healed using a triple antibiotic ointment
4 times a day on the nipples.  I tell the moms to wash the nipples gently
with soap and water before bf to remove the medication.

I don't usually suggest something that has to be washed off.  However,
I began to suggest this in cases of persistant cracks after working with
a mom who had this problem continually in the first week or two after
birth.  Her cracks would just start to heal and then open again, never
really going away.  When she developed a breast infection (probably from
 entry through the open cracks) and took oral antibiotics,
the cracks healed in 24 hours and never returned.

I theorize that there may be enough of a bacteria load at the site of
the cracks to keep them from healing, but not enough to cause full-blown
mastitis.

Barb Berges, RN, IBCLC