2014gl550

What is the small round thing next to air flow dial?

cyberorth

It's a dust sensor and is about to go off!
My guess is a plug to cover a hole.

ymmv

I agree it's probably a cosmetic cover over a screw, but it could be a sensor for sound or heat. Any dealer tech would be able to say for sure.
You can usually remove a screw cover with a spudger tool (appropriately sized/shaped soft/medium/hard plastic/wood/metal pick/pry/poke/ implement designed to apply force without scratching or denting.)