Weird black spot in screen?

[SunnyBagels]

There is a very odd looking black spot in the middle of my screen, and it started out as 2 lines slightly to the left of the middle of the screen. It has since then grown bigger and bigger, and is now a spot that nothing is visible through! It's really annoying and is almost the size of a pencil eraser. Could anyone please tell me what it is? ;-;

 

[CJM]

It may be dead pixels. I've never experienced that. But if it is, this may help https://play.google.com/store/apps/details?id=com.htc.chris.blackspotdetect

Tapped from a Nexus

 

[SunnyBagels]

I tried the app that you mentioned! I used it 3 times, but it didn't work ;c I guess that the screen is going out? Thanks for your help anyways! ^w^