green dot at top right corner of screen

All day for the past few days, there has been a tiny green dot at the upper right corner of my screen. It (terrifyingly) reminds me of the camera indicator light, but I thought that was supposed to be in the middle of the screen. I have also closed all apps and disabled camera allowance to the only apps that ask for it, just FYI. When I swipe toward the top to bring the top bar down (as if to check the time or something), the dot then moves right next to the control center icon.

To add to this situation, my MacBook also suffers from a (allegedly) placebo virus. Poor thing. I keep getting notifications (supposedly) from McAfee (which I don't have and have never had) saying my computer is infected, blah blah blah. I get one of these around every 20 minutes. I think it could be true. I took the computer to the Apple Store, where the guys at the Genius Bar told me that it is fake, there is no virus on the computer (they have run a check) and Macs don't get viruses. This was backed up by multiple people behind the counter. They said nothing is wrong with it. So I took it home. But this green dot is making me think again.

Thanks to anyone that can help :)