so, as shown in this post on the face forum, injuries are prevalent in bjj.
You almost always hear about someone having to pull out of a major tournament due to injuries and having a replacement competitor go in his/her place.
I believe that although it is not optimal, there is definitely at least a few things you can do to take advantage of your time.
1) Watch a lot of videos online.
2) Go to class still and watch/video tape people roll
3) Post online and ask other experienced instructors questions about positions/moves you have trouble with. Chances are they will probably answer it for free.
BJJ should be approached no differently than a class you are serious about doing well in. Difference would be that hopefully you care about BJJ more than that class... lol.
Anyways, if you wanna discuss some more BJJ related topics, check out the BJJ thread over at the face forum.