Is there any way to fix it? Not sure if a glass polish would do any good.

Try mosquito repellent first. Spray it on and wipe it off, 60% it'll be like new.

Thanks, I heard about that for plastic lenses but not for glass. It is not like the haze you see on plastic headlights because it is not cloudy just yellowish.

You might try some rubbing compound.

If it turns out the lens is a plastic of some sort, you'll scar it terribly with rubbing compound. I've used polishing compound (with even finer abrasives than rubbing compound) on plastic to lessen gouges and even that left obvious but fine scratches. I assure you it would be unacceptable on a gauge, probably to the point of ruin.