It's difficult to say for sure from your photos, (I know this kind of thing is really hard to capture in pictures from experience) but it's possible this is a sort of screen damage. It's something I see usually in laptops with plastic or more flexible housings.
If something was set on top of the laptop with the lid closed, or it was carried in a bag with other items, then the display may have sustained some damage from the pressure.
It's unfortunate, but in my experience display malfunction of some kind is the only thing that causes this and you'll likely need a new display to resolve it.