What is this vertical line screen damage, what could have caused it? Is there a way to fix it?

[Randal33]

Hi everyone!
I discovered this vertical line screen damage on the IPS screen of my Lenovo Y700-15ISK laptop after wiping the heavy greasy dirt off the screen with a damp microfiber cloth.
It is a dark spot on bright surfaces and it looks white when light shines on it (such as the flashlight of the camera).
What is this damage, what could have caused it?
I accidentally dropped my plastic ruler on the laptop screen from approximately 30 cm above and at an angle of 15 degrees, and I wanted to make sure it did not scratch the surface of the screen, that is why I cleaned the screen. There is no visible scratch, the ruler is made of soft plastic. Could this drop have caused this damage? 
Is there a way to fix it? Thank you.
(The first two images are without camera flashlight and the second two images are with camera flashlight.) 

[Levent]

Looks like some sort of liquid seeped into the backlight filter.  Only fix is to replace the panel.