hi, i recently bought a cheap, used concert uke on the internet. it came with some really aweful sounding strings so replaced them with someone decent ones. the problem is that the G string slot on the nut is way to wide. seems the original G string was fairly thick and the new string is lot thinner, so the string moves side-to-side when i play it. should i replace the whole nut or is there an easy trick to fixing this issue?