sand it down, and repair the sandwich with PU-glue, if the bottom laminate is broken, it will be more work!
I would use a 6cm wide carbon strip and a10cm wide glass strip put the glas on top of the carbon, so its easier to sand out smooth,
The rail looks ok, since most of the strength is there.
If the guy who sold it to you knew about the damage and said nothing, i would demand a refund or compensation!
Check the bottom, rocker( with a long straight ruler) and check for water!