I nursed my son until his first birthday (I did the same with his older brother) and then weaned him from nursing ... he was fine with it because I had mostly become a binky for him anyway ... but my breasts, especially one, are now hard and sore and I don't remember this happening with my older son. How long until the pain and discomfort go away? It's difficult to hold him because the pressure against my breasts is very painful!
Have you tried cabbage leaves in your bra? I know it sounds ridiculous, but I hear it's supposed to help. I weaned really slowly so I never had pain.
If you develop a fever, call your Dr. immediately. Until then, maybe try standing in the shower and running hot water over the painful breast while massaging any lumps. It might relieve the pain some. You could also try taking Advil and some Benadryl.