MacBook Pro retina bubble (like scratches) on screen

Hi All,
I have Macbook pro retina 13" (late 2013) for over than 1 year.
Recently bubbles (like scratches) appears at the left bottom corner of the screen, it started from 1-2 small bubbles an then appeared more and more.
Macbook wasn't in contact with water or heat so I don't know from where it came.

Is anyone familiar with such or similar issue ?
Currently it is not disturbing but I'm afraid that it will spread all over the screen.

Thanks in advance for help.
Micha