Pretty sure those are plastic 'lenses' so you aren't going to be able to polish anything out if it's cracked/scratched. Even if it was glass you can't really polish a lens. Best to just replace that part, I imagine it's just a plastic insert but you may want to check with Thunderdrones.
Thanks top gun pilots.
I looked l, and it does not seem to have any protective discs on it .
I think there is a fault with Q/C as I gently started to clean other sensor with cotton bud, but stopped as it looked like it started to scratch .
Is this just me ? Weird
I just wonder if DJI will accept this as a warranty fault ?