my iPhone 4 fell and turned blank(black screen)

After accidentally dropping my phone, i noticed that is turned dark, i turned it on, thinking it just dimmed itself, but the volumes can be heard, and after a while of trying, i managed to turn it off, but when turned back on, all that happened was that it would turn to a light gray when opened, and black when closed, even when i unlocked it, it still was like that. All sounds can be heard, however sometimes when i click it sounds like I'm in the dial of the phone menu, anyone know how i can get it to get back to normal?