Suggest Treatment For Muscle Spasms After Metatarsal Fracture

i recenlty broke 3 metatarsals in my left foot a few weeks ago. i currently have a walkable plaster cast on which fully covers my leg from just under my knee to the tips of my toes (not that im game enough to try and walk on it just yet). I have muscle spasms throughout my whole injured foot. It happens day and night. I can't sleep due to this. i just about to fall a sleep then im shaken wide awake in pain. im worried that its going to do damage to my foot when it goes into spasmode i suppose my question is what can be done to stop this??? please help im going insane. no sleep = spelling mistakes so im sorry if there is any!!
thanks