What dilemma? You give him blueprints on how to make nuclear reactors right before WW2 starts. Explain that he needs to skip the internment camps and just air drop them all into the UK with or without parachutes. The British will surrender almost as fast as the French, precluding the US from entering the European theater.
Reactors are harder to make than bombs, so I presume you meant bombs. But let's go with your alt history
1) WW2 Germany maybe gets nukes because they're given schematics (remember Hitler is more or less why Germany lost WW2, so presuming you aren't in some closed time loop thing, even if you get him info he may still fuck up everything). He also sabotages their own scientific development because of his racial shit. Recall the US Manhattan project was originally in response to the fear of Germany getting nukes, so in this timeline if we presume it is known Germany has the info to get nukes, the US may accelerate development earlier. If your plan involves ensuring scientists who helped the Manhattan project don't make it to the US, then you doom the United States long term and are a traitor to the nation lol
2) Even with knowledge of how to make nukes, they still need to get sufficient enriched uranium which takes time. If the US is also developing nukes, then there is a chance for conflict (cold or hot) purely because of a race to get sufficient known quantities of it
3) Germany also needs to develop a high altitude bomber that can support sufficient payload to deliver the nuke and have a lower risk of getting shot down (people forget that the bomber that the US used to drop nukes actually cost more to develop than the nuke itself!). A miniaturized version a warhead that can fit on one of the V rockets isn't viable yet even with advanced knowledge, since you still have to build all the supporting infrastructure to make one and any delivery platforms.
4) Assuming they have nukes by the late 30s and a means to deliver them, Germany may feel less of a need to ally with the Japanese or the USSR. Japan may still do it's own thing in the Pacific and Pearl Harbor may still be attacked - US involvement in a conflict with Japan would still remain high. Not allying with the USSR means no truce for invading Poland. Stalin is paranoid enough to still bolster military build up in anticipation of an eventual German attack, especially if in this timeline Germany is still grabbing territory like pokemon cards.
5) To make the nuke a viable threat option, Germany would have to demonstrate its usage in a way that gives wanted results. Given the ramp up time to refine uranium, they may find themselves in a position similar to the US: Limited stockpiles for immediate usage, because the ramp up takes a lot of time. However, the second a nuke gets used, all the nations in the world will go into overdrive trying to determine response options, including how to get their own.
6) A British surrender due to a nuke drop on a town besides London might get a British surrender. The US may or may not respond immediately - more likely, they would want to make sure they get nukes to protect themselves. Germany launching a nuclear attack on the US would not be possible at this point: No bombers with range, no means of launching on rockets. This would give the US time to beef up defenses and get a nuclear deterrent.
7) Let's assume Germany forces a capitulation of Europe through threat of nuclear weapons. USSR is a wildcard: Stalin wouldn't capitulate normally, so Germany would have to use their limited nuclear stock to force an unconditional surrender. Let's assume some scientists still fled to the US and helped the US get nukes: You'd get a cold war with Germany. However, without the benefits of a post WW2 economic boom, the US would be far less rich and powerful in this alternate timeline. You'd lose the benefits of Operation Paperclip/taking the science know-how of Germany, the loss of 20ish years of unrivaled manufacturing dominance, the loss of the creation of the Pax America world order with the US led to it's enrichment post WW2.
At best you'd end up with a poorer US and a Nazi empire that most of you would probably never be accepted in. You sure owned the libs with that plan!