I think I might have broken my ankle or foot. What should I do?

See a doctor. If you think you've possibly got a broken foot or an injury that is significant, have a foot and ankle specialist examine you and order radiographs as an inexpensive first line diagnostic study.
See a specialist. You should see a doctor, an x-ray can be done to evaluate for a fracture.
Get in with a doc. If you think something is wrong and it is as severe as a broken ankle/foot, then you should be seen asap by a physician.