I told myself I'm going to cut this nice and tight but my saw wouldn't cooperate. The bottom looks like the wave pool at Disney world and the sides might as well be the Grand Canyon. What solution do you recommend? A shim, putty? Both? Something else? So sad. Sniffle.
Situations like this are where having the habit of acquiring a collection old tools pays off - a narrow chisel is what you need - I've got a couple 1/8 and 1/4 inch wide and they are invaluable for jobs like this. You can use a file to clean it up but a chisel is much cleaner and more accurate.
Either a new nut or the baking soda/super glue trick.