I'd agree that before 1944 is impossibly without a massive PoD, even having nuclear weapons available in 1944 or just earlier in 1945 can make a big difference if it results in Germany being nuked.
One possible change that comes to mind; if nuclear weapons are used on Germany might we end up not seeing them used against Japan? Also, if nukes become the weapon that took down the Nazis the anti-nuclear movement might be weaker as a result.
Nothing like busting a nuke on the Nazis to make nuke socially acceptable