Dano,
You need to fix this. If you squeeze the hulls and the crack flexes, it will become a problem. This means your seem has split, this is a common issue with Nacra's and an easy fix. First draw a line aprox 3 inches in width around the line. Next grind down all the gelcoat . Use a disk sander or grinder for this task. When all the gelcoat is removed, grind through the resin rich glass without grinding too much of the fibers. where the crack is grind all the way down to the core about 1" on either side. Don't grind all the way through to the flange
Cover the sucker and heat it if you can to dry the core and the split in the flange.

Repair step 1. Have a friend squeeze the hulls together so the crack opens up. inject epoxy with microballons about (about warm maple syrup consistancy) Release the hulls, some epoxy should squeeze out. Scrape off excess. Let this harden untill you just cant dent the epoxy with your finger nail. Wet out a 1", 2" and 3" wide strip of fiberglass cloth with epoxy and place over the affected area in order. Squeege out the extra epoxy. Place "Release cloth" over the effected area and smooth it out with a roller. Let this part harden untill it is sandable. Feather in the edges with the grinder. The fair it with epoxy and fairing filler ie west 407 or similar. Sand this down so it is at least 1/32" below the surrounding gelcoat. sand with 80-100 grit so the surface is rough.

When it is completely hard (2-3 days at 80 deg C) use non air inhibited Gelcoat, let dry and sand smooth

go sailing.

Good Luck
Eric Anderson