you might wanna try rubbing toothpaste on it in tiny circles using a teri clothe or something, thats what people usually do to polish out really fine scratches in glass. it'll fuck whatever u.v. coating's on the screen though. come to think of it, i don't think that'd work as it really only works on tiny scratches
If its on the plastic, then look for an epoxy the same color to fill it with. Then use superglue to seal it when it has cured for a time.
If it is on the glass, you might try rubbing it out, as sizone suggested. But you need to use a very fine abrasive and lots of elbow grease and don't forget to use a little water, as a lubricant, for the abasive.
My preferred method would be to just use superglue (they make one for glass). Apply it in very thin coats, letting each coat dry, until you have filled the scratch. If you are patient, and do a good job, no one should be able to tell its there.