Very little chance. While I think Russia would use them as a last resort if Russia itself was being invaded, using them in a neighboring country is a non-starter. That would 1) damage and contaminate the very territory they want to possess, 2) alienate permanently all the inhabitants of that general area, friends/relatives, etc.; 3) Send fallout over their own people just across the border, as well as their own soldiers in the general area. It is impossible to prevent that from happening with any degree of certainty. And internationally, even China would freak out about that.
It’s hard to come up with a scenario in which the use of tactical nukes results in anything positive for the Russians.