G string slot too big

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?

try to take something like paper and put a little bit between nut and string. violin players do that quite often.

I've used super-glue to fill in oversize string slots in nuts. Use masking tape to protect the surrounding area, fingerboard and peghead, then put tape on each end of the string slot and fill the slot with glue. After it hardens recut the string slot to proper size. I've done this on brass, bone, and wood nuts. Practice on a scrap piece of bone or wood until you get the feel for it.
Jude

superglue or equivalent gel or thick style is easiest. the best way to apply put a drop on something dip a toothpick or end of old string and dab into slot no need to mask that way. usually then you add bonedust.... a quick substitute is some fine arm and hammer baking soda....really no kidding...