I see five different potential causes for this to happen to your MacBook looking at your picture:
1: A sticker on the bottom-left corner of the MacBook's top-case
2: A sticker on the bottom-center of the bezel of the screen (covering the MacBook Pro logo)
3: A sticker on the bottom-right corner of the MacBook's top-case
4: A sticker on the top-right of the bezel of the screen
and finally (the most likely suspect):
5: A huge piece of what appears to be colored tape covering the webcam at the top-center of the screen
Due to the tight tolerances of the space between the screen and the top of the case/keyboard, it's not recommended to put any types of these things on the screen nor the top-case. Doing so puts pressure on the delicate screen and will likely cause damage, if not immediately, then likely over time.
See: Don't close your MacBook, MacBook Air, or MacBook Pro with a cover over the camera - Apple Support