I was practicing Mandolin in the garden this morning having tuned it first when suddenly the very top G string slipped of the Nut.
But it had not lost tension and clearly did not break.

When i looked closely at the Nut I notice that a tiny Gnats cock piece of the nut had broken off the side and at at the string groove to boot?

That is with out doubt what caused the string to slip off. I loosened the G string in question and when i looked closely at the nut I could still see the line of the string groove really only a fractioned of the edge of the groove had gone.

So I got me a hand held mini grinder and worked out the string grove until the string would sit there has prior to this par-larva happening.

I then tuned up the Mandolin and HEY PRESTO
it Tuned perfectly and sounded great has before .
I know I should change the Nut but I have just paid to have it set up and if I replace the Nut it will throw everything out.

What do you think folks change the Nut (More Expense)
Or leave it alone and see what happens? I was bringing it to Knockers but the likely hood of it happening again puts me off.