It's highly unlikely. Nuclear weapons are expensive, destructive, and there is hell to pay if you lose one. There simply is no reason to have one aboard unless you expect you are going to need one. Training for nuclear warfare is performed with dummies that are identical to the real ones in operation, except they don't blow up.

In the Navy, nuke-equipped ships may carry them in the event they should be victims of a peacetime attack and they are authorized to use them in defense. This used to be policy in the Cold War, today, I don't know. They also might have them available in case immediate retaliation is authorized against an attack on the nation itself. B2s are not likely to be part of a deterrence capability (other planes can handle that mission better) so it's not likely we keep a few up there all the time loaded for bear, like we do our B52s and B1s. They would be saved to actually attack an enemy, usually preemptively, and are unlikely to be armed with nukes unless war was imminent.