One Bit holder stuck in another

Were you using that in an impact driver by any chance? They can twist the shank making it difficult to remove.
Usually backing out a tight screw will loosen it enough to pull them apart. If not Estwing/Vice Grips combo.

-- Never trust a man in winklepickers

I’ve done the same exact thing when using an impact driver and a non impact rated bit holder, the soft metal eventually gets jammed on. The black holder is likely still fine, perhaps put it in a vise and back the silver colored one out with your impact driver (I assume that’s what you were using?).

After I went through a few non-impact bit holders I just gave up and have been looking for a decent impact rated version. You can tell the impact ones apart since they’ll have rounded corners vs the standard hex profile with sharp corners (or the package should tell you too).

-- Perilous to all of us are the devices of an art deeper than we ourselves possess. --Gandalf the Grey http://davidwahl.org/category/woodworking/