Samsung Galaxy J7: Purple-Green Spot on Screen - Possible Causes, Warranty, and Solutions

A month ago I bought a samsung galaxy j7. Somehow, two weeks ago, a small purple spot appeared in the lower left corner. At first it was gossamer, but after a few days it got bigger and purple-green (in the middle of green, on the outskirts of purple). I have the impression that from time to time it is getting bigger. It is most visible on a white background, when it is colored, it is not so obvious. In addition, once it is very visible, so dark, and at other times it fades and is barely perceptible. What can it be and from what? Because I did not do anything with this phone, I have fallen a few times, but can it be from that? And whether they accept it under warranty, or do they think it's my fault?
PS I do not know where to put it, so if I chose wrong (and probably yes) then I'm sorry

Hello. If you have a warranty, please report it, do not admit that it fell because the display is for exchange.

Hello, I have the same problem and I would like to know if the stain has widened and what happened next?

Hello. I have an identical problem and it looks like it is not our fault. The blur appeared after 2-3 weeks from the purchase at the volume reduction button. Bought in December 2017. Rosla ... in the middle was black and violet outskirts. Now the whole display I have black purple is already silent. Still, you can see something in the wider area, but in general you can not see anything in the sunny weather. Apparently there is a series of missing phones that we were lucky to buy