You are required to be honest, and as part of the PNP to declare an intent to reside. In other words, if they can prove that you intended to live elsewhere, than it would be grounds for revoking Permanent Residence.
Once one has landed, the Charter guarantees freedom of movement and employment. You are not stuck. You should, however, make a good honest attempt at succeeding in the province that nominated you. They only have a few nominations to give, and if you leave, you took one from someone who would have stayed and improved the province. That may have been a student, it may have been a great employee unable to get a work permit.
PNPs are an offer made in good faith, and they deserve your honest effort in compliance.