Chosen Solution
I woke up this morning and when I went on my phone, there was a black mark in the bottom right. Originally I thought it was part of the video I was watching but I come to discover that it wasn’t. It doesn’t appear in screenshots which means that is the physical feature that may be messed up and I have no clue how to fix it.
It sounds like you have a damaged LCD; you will need to replace the screen assembly. You can either bring it to a local repair shop or do it yourself with this part.
