Bob-

Judging from the photo it would seem that the damage is in the last foot of the board. If this is so I would make a vacuum bag out of one or more plastic trash bags and using a shop vac I would see if dry bagging the board compresses the tip back where it should be. Of course you should clear out any obvious debris that you can see or get to and sand down any really sharp and jagged edges. If the board seems to dry bag satifactorily I would then pour some slightly thickened epoxy (using silica) into the crack and re-bag it until cure. It looks like you would want to set the board on its trailing edge while curing. After that it would just be a matter of puttying and reshaping the outer surface. If the damage goes up to the root of the board (where it passes through the hull) then the actual structural properties may be in question and you'll have to re-think the repair route and weigh it against peace of mind and dollars involved.

Chris