We wouldn’t do much more than leave a shallow scorched crater on the moon that probably wouldn’t be visible with the naked eye.
The first nukes that were exploded on Earth in July and August 1945 were bright enough to cause a reflected flash on the Moon visible to Earthbound observers.
I don't know if the Moon was in the right position to catch the flash on those particular occasions, but Richard Rhodes in The Making of the Atomic Bomb wrote about it as if this had indeed happened. I have not seen it recorded that anyone was actually looking at the Moon at those instants; possibly on some of the later scheduled tests.