Kim Jong Unwell is trying to make his dick look bigger by allegedly testing a hydrogen bomb today.
The USGS detected a 5.1 magnitude earthquake at the Punggye-ri Nuclear Test Site. This is little bigger than their previous nuclear test, which would have to have been of an unusually small yield, maybe 2 - 10 kilotons (they claim 40 kilotons, but that's too large). This new test may have been 20 kilotons at most, and that's me being generous.
Remember the Minor Scale tests conducted by the US in the 1980s? 4800 tons of ANFO were detonated to simulate a small tactical nuclear weapon. This is the same range as the North Korean tests. Could they have been nuclear tests? Maybe. But they could just as easily (even easier, in fact) been fakes conducted with massive quantities of high explosives - $100,000 of explosives by one estimate, versus the millions needed for a successful nuclear program. These ordinary explosives could have been doped with radioactive isotopes to make it appear to be a nuclear test from satellite monitors.
Now, it is possible that this was a boosted fission device, in which a quantity of tritium gas is fused to produce fast neutrons to increase the yield of a small fission bomb. This is how the small-scale "dial-a-yield" bombs in the US arsenal work to achieve sub-kiloton yields for tactical use. This design is not a true hydrogen bomb, and could explain the very small size of the test that was just conducted.
Given the choice between the two, I would say this was a mass of conventional explosives masquerading as a nuke, so people think North Korea is a serious military power instead of the paper tiger it really is.
But all of this is really a side note. There's no evidence this is a weapon, let alone a deliverable weapon, instead of just a display. Even if they have devices capable of nuclear detonation, that doesn't mean those devices are bombs (the US Ivy Mike test was a huge, cryogenically cooled building, not a deliverable weapon). And even if they have real bombs they still don't have any means of delivering those bombs to real targets.