There's excellent way to tell if you have a crack, but you need a small pump to lightly pressurize the board. Basically, you remove the vent plug, put the tube coming from the pump in the vent plug hole and temporarily seal the opening with some plumbers putty. After lightly pressurizing the board you apply a bubble solution, like the kind small kids use to blow bubbles, and brush it liberally around the damaged area. If you see signs of bubbling, you've got some kind of fracture or crack that penetrates the boards skin structure. No sign of bubbles, you have no worries, and can simply repaint the area which was damaged.
Eva, the Boardlady, showed me this testing technique at her shop a number of years ago. I would recommend sending Eva an E-Mail (she's great about getting back with answers), and she can advise you on the best pump type to use and what sort of pressure level to use. You definitely don't want to over pressurize the interior of the board.