If you cannot see the fiberglass, it is just a cosmetic scratch, which I would expect it to be. So it wouldn't need to be fixed. The white is most likely just an abrasive scratch. I got one of those white scratches from rubbing my boat up against some metal scaffolding.
If you can see fiberglass, you should try and repair it because water will get into the fibers and degrade the properties of the composite. Here is a good link on how to do gel coat repairs yourself