I can't imagine Pakistan would want to live in an area of such destabilization. ISIS would never have enough money to make living with the fallout of a nuclear detonation (both literal and figurative) worth it for nations in that area.
Also, do you have any sources?
Here:
http://www.christianpost.com/news/isis-claims-to-be-infinitely-closer-to-buying-nuclear-weapon-from-pakistan-and-smuggling-it-into-the-us-139585/Pakistan is an unstable country. Previously there have been defections from the Pak army to various radical Islamist organizations, and there is a real chance of such incidents occurring in the near future. Even the transfer of nuclear weapon technology to the ISIS can be extremely dangerous, as the group will be able to create nukes using Uranium sourced from Niger.
That article you posted is about how ridiculous the idea is that ISIS could acquire nuclear weapons, not the likelihood of it. It starts with a claim by ISIS
in their propaganda magazine that they could do it, then goes through increasingly unlikely circumstances that would need to be true in order for it to work.
The Islamic State terrorist organization proclaims it's now "infinitely" closer to buying a nuclear weapon and sneaking it inside the United States than it has ever been, a "far-fetched" claim that's designed only to spark fear of deadly chaos on American soil.
...
The article readily admits that the scenario that was presented is a bit of an exaggeration, but still argues that given ISIS' growth in the last year and expected growth for the coming future, there's no limit on what ISIS' capabilities will be a year from now..
...
Anthony Glees, director of University of Buckingham's Centre for Security and Intelligence Studies, told the Daily Mail that the claim that Pakistan would sell ISIS nuclear weapons is a "beggar's belief."
"It would be suicidal for Pakistan to supply them and suicidal for ISIS to seek to acquire them — it would lead to immediate military intervention," Glees said. "However, it is possible that ISIS might try to acquire nukes from somewhere, but if so, all western intelligence agencies would be on the highest alert to prevent this."
The claim is not credible.