What Causes Swollen, Painful And Sore Nipple After Periods?

I have had a very sore right nipple for two or three day, have recently come off my period but the nipple seems swollen, hard and hurts a lot. Seems different to the other nipple and have never had this before, i'm 35 and have a little boy of two who i never breast feed. Is this something of nothing or should i see my gp?