If you nicked just the top coat (glossy finish) you will be ok. If the nick goes deep enough to have cut any of the graphite fibers it will cause a stress concentration and the rod will break under load. No maybe, it will break it's just a mater of when.
I have successfully repaired this kind of damage by adding a small section of an old broken rod as a splice to reinforce the area. Look at the FOAL site and do a search of 'rod repairs'. There is an excellent 'how to' article with step by step instructions to repair several types of damage. Treat this one as if it were a clean break type of repair, just skip the inner splice.
While additional thread wraps will add hoop strength, they won't do a thing for bending stresses. Since the bending stresses are parallel to the rod and the thread wraps are perpendicular, they just run in the wrong direction to fix this kind of thing.
It might be possible to purchase a replacement for just the damaged section. Check with the manufactors 'repair' department. I have found some of them to be very helpful and understanding. It might even be considered a warranty replacement.
In reference to JC's advice, don't cast a unfinished rod without adding a reinforceing wrap to the female ferrule. This wrap is essential to getting full strength out of the joint. Casting a blank w/o reinforcing wraps can split the ferrule. If you are really convinced it is damaged, you might forgo the destructive testing. It will be easier to add a splint now and the rod might not break clean but could delaminate and splinter.
In the future you might look into some 'rod bond' tip-top adhesive. This is a stick of hot melt adhesive that is used for tip tops and metal ferrules. You can heat up a guide foot with a lighter and rub it on the adhesive, then stick it in place before it sets. I have always had good luck just using 1/2" wide masking tape in several layers.
Good luck, this one might just get need to be filed under 'learning curve'