First disconnect the battery then the screen connectors. Check the board connectors for dirt of possible the foam surround on one of the pins. Check your screen connectors too for bent pins. If OK replace each connector making sure it's seated flat. Do that with each one then finally connect the battery. Before closing the phone, turn it on and see if it starts up. If not and you can still see the image it's either a screen problem or a knocked, damaged or failing baclight filter. It may be worth checking under the foam around the screen connectors for dislodged components too. Be careful as if there are they can stick to the foam.