Did you sprain it? If it's still swollen, I'd ice it a few times a day, take anti-inflammatory drugs, and keep a compress on it (ace bandage or sports tape.) The compress will give it some extra support.
For boarding, you might also want to try changing the angle of your bindings; the current position of them might be putting pressure on your ankle where they normally wouldn't.
If it's been a few weeks and it is still hurting though? If it's badly, you may want to go check out a doctor in case there is more serious ligament damage in there.