Fork/headset screws help!

Hey, I guess I over tightened the top cap and now I can’t get the black bolt out of the silver bolt.

Anyone know the exact name of the silver part in case I need to buy it new?

Will go to bike shop as soon as I can to see if they can help.
I already ordered a new top cap and screw combo cos the screw was buggered anyway. I cut off the black tubular part to see if that was causing the silver bolt to be unmovable.