Warped post, part of a deck
 

I didn't notice until I was done that the post of presure treated wood was warped, anyone know if its possible to straighten this while in place, or do I have to disassemble it...?

You should be able to wedge a 2x6 under the deck and replace the post.

Impossible to straighten a curled 4 X 4. The best way is to cut it out and replace it. If it curled above the outside rim joist then it's possible if your planing on covering it with vinly post covers to just set a level againt it, scrip a line and cut off what amounts to a wedge and mover the wedge that's removed to the other side.
When it comes to pressure treated lumber ever piece needs to be inspected in the store, Then let it sit out in the sun for a few days to see what's going to mess up as it drys before it gets installed.

Thanks for the information! This community is wonderful!

No way to straighten you must remove. This is a common thing with pt wood even straight boards at first will warp as they dry out. :(