there are a lot of home remedies for fixing scratches in screens. most involve resurfacing the way you would buff out a scratch in paint but most of these will do more damage than good . They usually will make the scratch smaller or lessen the severity but at the expense of the surrounding area, making it duller . The only way to truly get rid of the scratch is to replace the entire screen with a new one .
http://www.makeuseof.com/tag/insane-tablet-and-phone-touchscreen-repair-tips-you-should-avoid/
Hope this helps