He doesn’t have a weaponized nuke yet. It is a pretty big step to go from test nuke to a nuke that fits on the end of a missile, is properly fuzed, etc. It should be a bit longer before he can launch a nuclear armed missile.
A nuclear truck bomb or container bomb is a possibility, though.
Sounds like he declared DC to be the target.
If so, that means unconventional delivery (not missile). A yacht or a fishing boat would be easy to get close enough.