Why is there a semi transparent oval at the bottom of my screen and how do I get rid of it?

[AC Question]

No matter what app I am in or where I am on my phone, the oval is still there. It's on every screen. When I turn my phone sideways and it goes into landscape mode, the oval moves to the bottom of the screen in landscape mode. It won't go away. How do I get rid of it?

Here is a link to a screenshot. Take out the spaces in the url. I am a new poster and I'm not allowed to post links until I have 10 posts.
http : // imgur . com/db0g4x5

Any help is greatly appreciated! TIA.