My ps3 cant read my cod5 disk afther i downloaden map pack der riese but there is small scrath on the disk?

but my ps3 can read orther games but it cant read call of duty world at war there is a small scrath at the disk but it to smal to make in imapct so help is my ps3 or the game help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!… first 1 hu answers it right gets best question