Looks like something for indicating mouse direction using side buttons or maybe tilt wheel.
Recently I've noticed a small icon stuck to my screen always in the same spot regardless of what program is open. It does temporarily disappear when I restart my computer but it always comes back after a while. I took a screenshot of it up against a white page and crudely circled it so you can clearly see it here. I'm on Windows 10, how can I get this to go away? Thanks!