Ouch. Take it in to Apple - they almost always replace them for free. In the unlikely case that they charge you for this or if you've already had them replace the screen for free in the past, the backplate replacement is only $29. Good luck and post back!
go to walmart, and buy a wrapsol kit, its a silicone type of film and pretty thick, so the broken glass will not cut the film, if you like tht cracked look, the film will keep it all in place. Full kit comes with front, back and around the frame film. I use my iPhone with a full kit, love it! dropped a couple times.