I sprained an ankle when I was about 15, I turned it while doing a skid on my (whatwe would now call) mountain bike (this was 1978) and it was a couple of days before it was back to normal. It hurt like hell, I couldn;t sleep and I couldn't walk on it, but it healed quickly (of course, I was young then and quick to heal). I also broke an ankle when I was about 25, and that started like a sprain, or felt like it. I could tell it wasn;t a sprain, though, when the swelling started to bruise. That was bleeding from the bone.
I spent a long time trying to convince myself it was a sprain, even when I knew it wasn't. I still can;t properly point that foot all the way down, and it was treated professionally. It doens't gein the way of cycling, though I'm always expecting arthritis or such like as I get older.
I'd get it checked out properly if I were you, just to make sure, and after that, do your falling on alternate feet, just to be on the safe side