You should check the ribbon cables. If one appears broken, you need to find a replacement. Otherwise, your screen is probably cracked internally, and will no longer function, at which point, you'll need to find a new screen. Which model is the phone?
You'll likely just need a spludger and a new piece of glass. If the screen itself was damaged, though, you'd need specific screwdrivers, as well. If the frame around the screen is bent, you'll need to bend it back into the original shape.