Possible Hairline fracture ?!?

I hurt my ankle over christmas break at gymnastics.. it still hurting me. it was only swollen for a day or so and i didnt go to the doctor. My gymnastics coach gave me an air cast to wear for a few days to build it up again. But now it still hurts a lot. Im going to the doctor the 15th to have it looked at... Im thinking its a hairline fracture. And thats what my coach thinks too. If it is.. are they going to put me in a cast, or maybe a walking boot ?! and for how long ? PLEASE HELPP ! ):