Why Do I Have Pain in My Nipples Years After My Breast Reduction?

During the mid 1990s I had a breast reduction because my breasts were so large. I am very happy with my reduction except for the fact that at different times I will have severe pain in the nipple area and in the scar that runs from the nipple to the lower part of the breast. It is mostly when I get cold. This can happen at any time of the day or night and can be very painful and hard to get rid of. Any suggestions why this happens and what I can do the next time it happens?