Sorry about accident. Like the advice about trainer or other inside exercise while recuperating arm.

if you have a cast might not want to sweat too much although important to keep in good shape without risking arm (assume Apple made "left" a "jet"). Can you walk and will walking give you your exercise?

Besides a recumbent there are techniques for falling off a bike we should all know and do to lessen damage in some situations. Believe the experts suggest keeping arms on the bars and feet in the pedals and assuming one wears a helmet. Of course none of us are accident proof.

we all react differently to these situations. I have a friend who would ride regardless of the risks as riding is so important to him. YMMV.

Ed