I don't think they have sufficient conventional munitions to do that (as they already have dropped fire rate due to shortages), obviously they have nuclear weapons, however there would appear to be significant geo-political risks to using them.

I'm not a politician so I'm not sure that they won't do it, I doubt even the politicians are sure. However the alternative would appear to be for neighbouring countries to just keep giving russia whatever it wants, and I can understand why those countries are not happy to do that.