We've all done it! Launch your freshly varnished woody and next thing you know----POW right into a dock. If there is a dimple in the wood and the stain has not been cut through, there may be a relatively easy repair solution. One approach is to rigorously sand the area, through the varnish, stain and the wood until the "dent" disappears. Then you must restain the sanded area which is difficult to blend in with the rest of the plank. The easier way to fix the dimple is to fill it with gel viscosity super glue. Spread the glue with an auto body filler spreader, wait for it to cure,then sand flush with the rest of the plank. Again, this only works if the stain is intact.
I found this idea on the ACBS website which, by the way, has many helpful videos pertaining to the maintenance and upkeep of wooden boats.