I agree get to the vet asap! But DO NOT SPLINT the leg to the body!! Without knowing the severity of the injury or the location of the break you will only risk further injury, and more pain to your pet. Also if you move the leg the wrong way, you may spook your beardie causing him to thrash/run away. Your BD should be able to keep his own weight off the leg, and favour his good arm. If anything you could try wrapping him in a towel just to keep him still. Adding support to the injured leg without moving it may help him relax a bit until the vet can ascess the situation.