I just did something like that last week. I taped the area around the nut, then put a drop of superglue in the string slot, and then filled it with
Microballoons , topped it with another drop and let it dry. I read this somewhere that people use baking soda (powder) instead of the microballoons. I think they both serve the purpose, which is just to give the glue something to grab-onto and give it a solid fill.
Anyway, once it dries, then you can file it down to where you need it to be. I actually did all 4 slots as they were all a little too low.
Seems to be stable, but I don't play professionally. If I did, I'd probably put a new nut in just for piece of mind.