I understand your concern about not wanting to gain weight but a broken bone usually heals in 6 to 8 weeks, and then you can get back to what you did before, doctor’s clearance assuming.
Why don’t you use this as an opportunity to try out different exercises like mat Pilates which is floor-based and does not stress your leg.
Give your body a chance to heal; It is okay to take is a bit easier for a few weeks.
I agree with Michael. Consult with your physician first and you could always do some upper body workouts. Other than the typical upper body exercises which you can do by using dumbbells, tubing and machines, try to add to your routine some battling ropes (upper body), medicine balls, TRX and punching (as long as it doesn’t stress your leg) as well. Maybe swimming can be another option for you.
I hope this helps.