I would also do a fluid flush, that's fixed whining on a couple of different cars for me. If you don't feel comfortable and don't went to pay a dealer to do it I think any quick lube place can handle it for pretty cheap. Just make sure they use the proper fluid, it says on the cap what to use, but you never know.

Whining power steering pump: seems to be a Nissan trademark. Both my 370Zs did it as did my '04 Altima, as does my neighbors '15 Altima ......

Whining power steering pump: seems to be a Nissan trademark. Both my 370Zs did it as did my '04 Altima, as does my neighbor's '15 Altima ......

and my 06' Xterra.