Dropping a diamond disk on it's edge is about the worst thing you can do to it, but it depends on how bad the drop was as to if it is destroyed or not.
If the edge has only slightly crinkled and the electroplating has not detached from the disk, then you may be able to hammer the crinkle back down and have a perfectly usable disk (I would still recommend avoiding the edge when you grind with it though).
If the electroplating has begun to remove from the copper substrate on the disk, then you're much better off buying a new disk and throwing this one out. That thin layer of nickel will act like a fast moving razor blade when you try and use the disk on a wheel and grind with it. That's a very dangerous situation and one you don't want to mess with.
Buy a new disk and chalk this one up to a learning experience.
If you're unsure of the extent of the damage, send the disk back to us and we'll either fix it or let you know that you need to toss it.