How to build around metal column?
I would have notched the top plate of the piece of wall that is abutting the steel pole.  The goal here is to provide a flat plane and nailing edges for drywall.  

Assuming the post is the end of your wall.  Since the steel post is proud of the edge of the 2x4 wall on one side probably the easiest thing is to cut strips of ply that pull the 2x4 wall to the same plane as the steel post.  I'd laminate all of the 2x4s by 1/2 or 1" whatever that post is proud of that side of the wall.

Then put a 2x6 ripped to the width of your new laminated wall and cut to the height of the post notched to the steel plate at the top.  I'd PL premium the 2x4 to the post and steel plate.  Sill gasket the bottom as there would be no pt plate.  Then you can drywall per normal such that the post is embedded in the framed wall.  I'd probably redo the top plate of the wall that approaches from the other side of the steel post so the drywall can be nailed all along in the same line.

Good luck.