That is odd. It looks like a tiny "x". My first thought is that it's related to ads. It reminds me of a small x you would see to close an ad.
Then I noticed that in both screenshots you were using a web browser or possibly the forums app in the second shot?
Are you only seeing this during online activity or in certain apps or is it everywhere on your device?
What happens if you click the little x? I thought perhaps you have an app that is causing ads or it's a problem in your web browser causing ads but it looks broken, like the ad isn't actually showing up.
If it's only in your web browser, you might try clearing cache and data on your web browser app in your device settings. Other than that, do you have any task killer, battery or ram optimization or 3rd party flashlight apps installed? Some of those are notorious for adding weird things to a device.
