you can also check for visible scratches on the disk. It may be causes by those. if so, return the disc.
If there is some filth on the disk, take a soft piece of cloth and wipe off the dirt. Do this by wiping from the centre of the disc to the outside, so in a straight line inside out. Never wipe sideways.
If you have some polish lying about, yu can also try polishing it if replacing it by the vendor is a lot of trouble.