In pain

For some reason my ankle - the one I sprained two years ago - is really, really hurting me right now. Feels almost like a fresh sprain (not that bad, but the same kind of feeling) except it's not swollen and I don't remember falling or anything like that. I walked from work to the gym, did my circuit, walked home from there, and an hour later - pain!

No clue, but I'd like it to stop now, please.