Headset/Stem confusion

[Jordan1640]

Hello.
I've recently rounded off a screw (pictured) and firstly I'm confused weather that part comes with my headset or my stem? Also can any headset fit with any stem?
I'm sure I could just buy a new screw but I'd rather buy a new headset.

If it helps I have a Social Narc 2013 bmx and the stem is a social freeloader it says the headset is just a "internal headset" now I don't know if that is internal the brand or how it's situated.

Any help would be great

Thanks
Jordan