How likely is it that my ankle is broken?

Alright, so to me it sounds like your ankle merely had a good meeting with the ground, haha. Your ankle bone, the part in between your calf and heel, is sore, and may remain so fro a few days. If the pain doesn't go down (with icing on and off all day for 10 minutes each hour) within 24-48 hours, then you may want to take a trip to the doctors. Also be sure to rest and drink fluids, eat a healthy meal, etc etc.