Have you talked to your doctor about your ankle ? If not, that really is the best place to start. For now, you may want to continue laying off any running until you're absolutely sure the ankle is healed. Right now, it may still be weak and if you try to run, it could end up swollen again.
Depending on what your doctor thinks, you may have to lay off any running til the race. resting for two weeks might be the only way to make the race. but it means you may have to do a walk/run combo. that's not a bad thing. many runners have done walk/run combos.
Because of this injury, you may have to wait for another half marathon to really compete. You definitely don't want to run on a bum ankle.
Continue to rest, call your doctor and see what they think.