I stubbed my toe and now it's black and swollen. doesn't hurt much but i have a dance tomorrow. what to do?

Be more careful: Unless you have peripheral vascular disease, ice is your friend & will help. Blood under the nail should be released it as soon as possible after the injury using a hot paper clip to make a hole in the center of the nail or better yet - have a trained health professional do it. Ibuprofen and Naproxen will help with inflammation. Let pain be your guide. If its hurts too much to dance then don't.

See a doctor: Your symptoms would deem avisit to the podiatrist to see if the toe is fractured or how severe the injury is if it is black.