Hi,
There can be several possibilities that could cause nipple pain,which is usually not a common symptom of breast cancer.
It could be just skin irritation caused by clothing,allergies,infection or hormonal changes particularly if you are going through menopause.Your breasts/nipples may feel like they did when you went through puberty and much like they did during the first trimester of pregnancy.
If the pain is excessive and you are worried about it,it's better to see your Doctor for a clinical examination to find out if the discomfort could be caused by some other underlying problem.
Best wishes....