A ding on the rail will make the board susceptible to breaking. You now have a broken board. Don't let a split in the glass on the bottom go unchecked. I have seen the entire bottom glass ripped off because water was forced into a little split in the glass. Dents in the deck, which are commonplace with today's surfboard construction, should have a couple of layers of glass put in the dent before it delaminates.
Delaminated glass is far more expensive to repair than reinforcing the existing glass.