What the beepbeep?
If you still want to take part, jon, I suggest you rest your ankle completely for 2 1/2 weeks MINIMUM. Preferably at least 3, of course. Then maybe take a short jog. 4km? 8km? Whatever you feel up to and see how. If really cannot then never mind. Can run together next year. Ankle is more important.
The above is not due to any medical knowledge. It's something called common sense plus a lot of optimism. Heh. Hope it recovers soon! Don't stress it by walking around too much!