You would have to get a replacement, they cannot be repaired. Initially I would try whoever created the program and see if you send the old disk back if they will replace it, EA Games did that for me when one of the games disks cracked. If thats a no go then you would probably have to pay for a replacement.
And if it has a crack in it I would stop using it now. If it breaks in the drive at high speed it will shatter spreading little bits of plastic all through your drive and computer possibly destroying the drive as well. Happened to a friend of mine with a brand new disk I can only assume the plastic was faulty as there was no sign of any cracking.
Only other idea is try to copy it and use the copy, though that may not work due to copy protection on the disk.