Sore spot on nipple

joie12

There's a spot on my nipple that is red and achy, on the top where her top teeth hit. Nursing brings sharp pains, unless I put her in a football hold so that she's not in the same position as usual. It's only on one side. Her top two teeth just broke through a few days ago, but I can't remember her biting me. Could it just be from a poor latch? If so, why would she just be getting a poor latch now, at ten months?

Edited for clarity