Do you honestly think it would have made a difference? The only way that Ukraine could have got away with a defensive nuking of Russia would be if the entire West backed it up. The fact aside that we've done a shit job of backing up Ukraine in this timeline let alone that one, nuking will always be a highly controversial move. I doubt there's a single situation where most of the civilised world would respond with, "well, they did deserve it...".
IMO the only scenario where having nukes makes any sense is if you're the only country with them. That ship sailed a long time ago.