Movement of nuclear material is covered by non-proliferation treaties. If the west comes to know of any violation, Pakistan will suffer heavy economic punishment. All the Paki Nukes are as a result of kind courtesy by the Chinese. Therefore Chinese permission is a must. No way China will OK a proliferation move.
Nukes require a delivery system to be effective.
The Sultanate does not have one. Therefore Nukes are useless for it. Storage of Nukes is not an easy thing. It is very expensive and carries a heavy environment and safety risks. Building such storages is an unnecessary expenditure for the Sultanate and I doubt, if this has been done.