Accustic wall panels

[bearC]

I want to put accustic on the wall behind the bed. I've ran into a little is where the corner isn't straight, level, plumb. Sorry unsure of the correct terminology

What would be the best way to approach this?

It's about 15mm difference at the top

 

[Wayners]

Put an end trim where your green line is up wall cut so its wider at the top maybe.
Could always straighten that corner which is a bit more involved