Oh. OK .. I see.
I thought it was supposed to be all metal.
As a repair, my guess would be that it's going to be horrendously expensive(for Nikon) to fix, as it'd require full strip down and replacement of the inner tube.
Of course I don't have this lens myself, but going by those low res smartphone images in the link, it almost looks as tho the filter thread area may be a removable part. One which may be removed to replace the front element. Traditionally, this is held by an inner ring with two notches at opposing ends, which requires a special spanner to remove.
But those two notches aren't obvious(or visible) in the link. So it may be that (contrary to my previous text) it may not be as expensive as it may otherwise be.
If the front most end of the lens is removable as described, it may only be a few hundred dollars to repair.
Remembering that I know very little of this lens on a personal level .. I've only had brief opportunities to play with it tho here and there .. I'm just trying to lessen your levels of stress, until you get a repair quote.
Beyond that, you're on your own
I'll see if I can dig up any repair info on this lens.(I'm curious now).