There is a blue drip on my screen that I can't remove. What the neck is this thing?!?

About three-quarters of the way down on my screen on the right hand side as I'm looking at it there is this medium dark blue drip shape thing that just started on my screen I have no clue what it is and I've tried everything to get it off and I can't what is this thing is it the black plague for Android what is going on

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