I have a second hand twin tip that has been scratched on its edge from being run up on the beach. How should I repair this or should I not bother? Will there be any noticeable difference.

Just turn your foot holders around the other way so ure heel side edge is fresh

^^ flyingcab is right, ONLY if you board has inline inserts (a lot of boards dont)

If it is just small superficial scratches then a light sanding will be fine.

Post a photo, will be able to tell whether to worry or not.

Photo? Then we can proceed with instruction

keep running it up the beach, but on finer sand. Then it will sand the big scratches into fine scratches