If it ate into it, it's beyond help. If it just made a surface stain, try Novus Plastic polish, 3 is coarse, 2 medium, 1 is for finish. If it's too much for 3 to help, start with 400 wet paper, than 600, than 800, than the Novus. I've fixed a bunch of damaged gauge screens for diving & when done you would never know there was damage. Takes time & patience but little money.