is there a way to do it, maybe by filling in with a little resin
Depending on how big the dents are you can cut out the glass and some foam then put more foam in and reglass as normal or, if the dents are small then just fill in them in with resin. The latter may screw up the weight-balance issue on the board depending on the size of the dents. Personally, if it isn’t worth putting in new foam then it isn’t worth filling with resin.
If your not to concerned with weight sand the glass really well and just re hotcoat it it will fill alot and also give you a better base for your gloss http://www.paradoxdistribution.com