White and Grey screen with pixels

Even tho my sisters phone has a crack on the screen (dropped about a week ago), it's been working fine until about an hour ago, I've tried resetting it and it's still the same, does anyone know what else could it be, the screen still works and you can still see some of the stuff (the camera doesn't pick it up well) , but I can't get rid of the white and grey stuff, I don't know what it is can anyone help me?