I just thought I'd mention this to see if it rang any bells: since I'm not a serious dancer, I won't be bothering to get medical treatment or anything.
For some months, I've had an intermittent pain on the top of my foot, where the toe meets the foot. It feels rather as though someone has taken a hair, wrapped it round the base of the toe, and pulled it very tight, so a very thin line of pain. I only really ever notice it sometimes when I'm doing class, and particularly when I'm pointing the foot or have the foot up on the barre. It was originally the middle toe, then it moved (shifted,