I have the same thing on my IPhone5c it have black spots on it and it want let me do nothing i tried to do everything and I went to put some water on it still did work so maybe try clicking home button 3 times or Try clicking the Home button 3 times (really fast). If that doesn't fix it, go to Settings/General/Accessibility/Triple-click Home, and select the "White on Black" option. Then, triple-click the Home button.