Probably not. The biggest weapons that its practical to smuggle in are the aledged ex Soviet Suitcase bombs which are rather small devices (to the extent they exist at all).
Anything bigger would require a ship or plane for delivery, and those are getting pretty close scrutiny these days.
Military nukes are a whole lot smaller than you think. What once in Hiroshima took a plane to drop, we now shoot out of a cannon and it is a lot more powerful.
Think cannon shell, and then think lunch box.