Ouch! feeding woes?

My son is only 12 days old. I have been feeding so far, but all of a sudden since this afternoon really my right nipple has been KILLING. Not just to the touch, but just when I'm sitting down, walking around etc. It stung when I tried to feed Max on the right so I've just been doing the left today. What could be wrong with my right side? It's not a latch problem, it just hurts all the time.