Depends on how deep the scratch is.
If it is just superficial and hasn't gone through to the core, then you should be alright and it will just be a bit of a eyesore.
If it has gone through to the core however, you need to get it fixed because if water gets into the core of the board it will swell and warp and ruin the board.
I'm sure there should be some repair places near you that won't charge too much to patch it up for you. We've all been there though, kicking yourself afterwards for kiting on such shallow water. Hope it isn't too bad.