As others have said, I very much doubt that Russia will escalate to the point of nukes unless NATO gets directly involved, and even then it might not happen depending on how things go. There's simply no real motivation for Russia to do so. Putin and his government are very well aware that usage of nukes is an extremely desperate ploy and thus should only be used if they're losing, but they're not only winning, but prospects are currently the best they've been in over a year because the Donbass front is finally collapsing.

I'm not even really worried about the usage tactical nukes in Ukraine or whatever, because what would the point be? What would they achieve that conventional explosives and attrition cannot? Ukrainian forces are already dispersed because of the threat of drones and missiles; there's not some giant parking lot with 500 tanks on it to drop a nuke on. The only thing they'd be potentially useful for are a) hitting airbases to deal near-irreparable damage to them (against what Ukrainian airforce? the F-16s aren't doing very well) and b) hitting Ukrainian cities, and Russia has kept civilian casualties very low compared to Western wars, displaying that they do not share the West's utter disdain for civilian life.