I’ve done a lot of kayak, waveski, surfboard and SUP repairs. From experience I would probably just leave it alone. A lot depends on the construction, is it expoxy on the top coat? is it polyester (lots of boards have a polyester top coat), is it carbon with a abs/polyethylene finish). I’ve gotten to the point where I just use a rattle can spray paint (Krylon I believe) to color repair spots on my SUS boards, and a hot coat of epoxy if they epoxy boards, My favorite now are kevlar/abs they are carbon with distressed white finishes, so ghetto look doesn’t hurt anything. Adding a full layer of paint and a top coat, adds a lot of weight to your board and in a year or two will look like crap, so my advice is just clean it up, and go paddle.