Maybe not nukes. Too nasty for everyone and not really required. But all restraint would have been removed. Up to this point, Putin has been keeping the military operations on a short leash, strictly concerned to attain a high exchange ratio in order to demobilize Ukraine. Territory was secondary; the land wasn't going to go anywhere. But now, pushing the Ukrainians back to the frontiers of the Novorossiya oblasts is preparatory to consolidating sovereign control.