Only when crashing into the ocean, thousands of miles short of its target
Edit: seriously, though, it’s pretty clear that they can build nuclear warheads (how many and what size is unclear), but their problem is getting the bomb to its target.
Rocketry is hard. It’s uber-expensive, and it requires a great deal of trial-and-error. I wouldn’t be surprised if they had gotten data, etc, from Russia and China like some guidance (or even rocket plans), but NK’s best physicists and aerospace engineers are both: not that great, and working entirely alone with a budget that is a minuscule fraction of anyone else who has tried this.
They’ve been trying to launch an ICBM successfully for almost 2 decades. They haven’t had much success yet.