Hate to be a doom-sayer, but have you had it checked up properly?
I thought I had sprained my ankle a few years ago, hobbled around for 2 days determined it was going to repair itself and finally had to give in and admit it was more - turned out I had a spiral fracture of the smaller of the leg bones (the fibula) very near my ankle.
If you've done that it hurts like hell but doesn't affect the stability of the leg. I didn't need surgery, but a few weeks in a strap-on cast and crutches... all better now though.
So just a thought - get it checked up