If there is anyone who will use nukes in Ukraine it will be NATO. Just like they planned to use nukes in Germany back in the Cold War.
Back then the plan was that when the Warsaw Pact concentrated forces to do a city assault, they would just nuke the city and kill both the civilians and the Warsaw Pact troops. The US had plans to do this, and so did France.
Russia will not be using nukes right next to their border. They can continue escalating conventionally if they want to. They can do carpet bombing for example and thus far they have refrained from doing it.