How to fix a scratched cd?

i was playing on my xbox 360 the normal one...and then the the xbox fell over on its side and as u know the game got scratches on it and now it wont work... how do i fix it? it says disc is unreadable .by the way i bought the game from target and not gamestop i dont think they will replace it... will they? and dont say that im dumb to buy a game from target and not gamestop