I don't use metal nocks anymore, and make my nocks out of serving. I think it makes a better nock anyway, and may help with your problem.
In "Become the Arrow," Byron Ferguson illustrates his way of making tied-on nocks. He just ties a series of overhand knots, alternating the knots on the top and bottom of the string until he has enough to make the nock. Rick Welch uses a method that produces a more finished looking nock. He ties the same knot that is used at the very end of of the string serving to make the nock. It is kind of a complicated knot, but if you know how to serve the bowstring, you'll figure it out.
Whatever knot you use, if you use a contrasting color of serving to tie the nock, it will be easier for you to see when you shoot the bow.
Both Byron and Rick say the knot can be adjusted by screwing it up and down the serving until you have it in the right location. Then when you have it in the right location, you dab some superglue on it to hold it permanently in place. Maybe you can screw it up and down the serving; I wouldn't want to contradict two of the best shots on the planet. But I find it easier to just shoot with a metal nock (lightly crimped so it doesn't crush the serving) until I get the right location. Then I tie on the bottom nock, then I remove the metal nock, then I tie on the top nock. Then if the fit is right, I dab on the superglue.
You can still cut off the tied-on nock without damaging the serving even after it has been superglued, if you change your mind and are careful about it. I use a single-edge razor blade and cut parallel and just above the serving.