I just recently got my cast put on. It is a short arm cast that goes around my thumb and down to about the center of my forearm.

I am pretty sure that it will not be off by Halloween, so I am looking for some unique or original costume ideas. It would be good if the costume could either hide the cast (make it unnoticeable) or, better yet, use it as a prop.
I would prefer something age and gender appropriate; I am a 17 year old female.

Any help is appreciated!