My best friend had a bone shattered in his hand/wrist about ten years ago. Unfortunately, he had to suck it up and take time off, as there simply aren't too many ways to safely train around an injury like that until it has properly healed.
My friend was natural, carried a good bit of muscle, and was about 23 at the time. He kept his diet good, and hit legs and cardio harder. Honestly, he lost barely (if any) upper body size during that time.
The setback probably seems devastating to you now, but healing completely should be your primary concern. Don't rush your recovery by doing something that will hinder it. You obviously won't gain new upper body size over the next month and a half, but anything you lose will probably be negligible at worst. And, you may be surprised at how quickly you rebound!
In the meantime, this will be a good chance to give those muscles a rest, and you may find they have a more sensitive response when you start up again.
Good luck with your recovery and future progress!
yes i agree with Monty and Wooo...itīs a small set back that in some weeks will be over. What you do now will affect your FUTURE training...REST it and do cardio like Monty said.