As your fracture is already fixed ,you need not worry about displacement of fracture or of non union at all. After any fracture fixation ,It is advised to start active range of motion exercises as early as possible.
This prevents the joints from getting stiff, increases blood supply to the fractured bone and thus helps in better healing of bone. This movement exercises do not hamper callus formation in any way but in fact they encourage callus formation and early recovery. If the fixation is good you need not worry about the bending of bone on exercising.
helps, but ask you physio to be gentle
You should use walker for your daily activities without putting weight on the operated limb. You can take a physio help for that.