Easy repair, but you do need to get the stuff which makes this even easier to repair, but first clean up the damage removing any loose carbon shards or bits bent back above the original surface line, use a needle file and rough dry grit cloth of around 200 grit, then buy this!
next day delivery off eBay, get the dark grey colour epoxy, which is really close to the black of the mast, this stuff is great for the Moses wing damage you may get as well, the good thing about this product is you can mix and introduce a good layer of the epoxy mix pushing the stuff into any cracks or air holes or solid rough but clean surfaces, then wait,
after a minute dap the excess mix of resin to see how near it is to setting, when it gets near putty texture add a bit more of this to the repair area and then wet your fingers, and work the resin gently to get good and near the profile shape, but with a little excess that can be removed very easily quite soon after with 400 or 600 grit wet paper, go gently with the wet paper wrapped tightly around a small wood block,
if the resin is too soft it will wrinkle a little, stop and quickly use a small hairdryer to soften the surface even more and use wet fingers to smooth away the wrinkles, very quickly the resin will go very hard, use finer 800 grit wet paper and gently go back and forth along the repair to level it down to the original good mast edge parts, don't worry about the small scratches you will leave on the shiny part of the mast, but don't go too hard into the surface, keep things light, then leave the repair for a cup of coffee, after the coffee break go back to the repair with 1200 wet paper and then 2000 wet paper, this will remove all scratches,
for the final blend in and polish use a 3000 grit round foam pad, not to be wetted! Keep this very dry and rub all scratches or dull areas untill they shine back, I do use 4000 grit round foam backed pad for this final finish, but I use these pads to maintain the leading edges on my mast and wings, every foiler should have all this kit I have mentioned, along with the acrylic Matt spray paint shown, this spray paint fills any tiny air holes and tiny scratches, apply 3 light coats for a even smooth finish, leaving only 30 seconds between coats, dry with a hair dryer and leave for one hour, after which you can finish the surface just as above but starting with 1200 grit wet paper, no negative paint reaction with Moses paints or laquer, and primer is not required on moses carbon wings or masts.
the foam backed round pads are available off eBay along with the dark grey (black in my view) 4 minute resin,
The pads and acrylic paint are all available from any car paint shop, of which there are around two in most town areas, and are open to the public not just repair garages, and are super cheap compared to eBay and halfords,
Pads link here--