Ok so what you need to do is apply ice to the injury. Once the broken bone is immobilized, apply something cold (preferably ice) to it as soon as you can while you wait for the ambulance. Cold therapy has many benefits, including numbing the pain, reducing inflammation / swelling and reducing bleeding by causing the arteries to constrict.

AAAAAAAAAAAAUUUUUUUUUUGGGGGGGGGGHHHHHHHHHH I NEEEEEEEED A MEDIC BAAAAAAAAG