As of the moment, apparently the UI is broken and as such there is no use option as there should be and will be when they fix it which you said indirectly in your post so this if for others more so.

I have gotten two, neither are marked under the achievement, and I'm not wasting a slot to save them so I sold mine since they can't be banked to put on a mule. Chances are this is the same for you and you need to decide if you want to hold it until you can use it or sell and go get another someday which may take a while and bore some players. But you can double check looking in your achievements for that greyed out slot turning white I assume.

Also don't bother asking with the "get help" function. They give you a generic response that says to go look on their FAQ or to look in the forums only. Just hope people keep bumping this enough with their thoughts/experiences until a mod finally gives a slightly more useful response such as if they are aware of the problem AND if they are fixing it before they deal with launch server issues which may put this off for a good while if not which is okay, just nice to keep the players informed to plan what to do with our limited backpack space.

Having the same issue on xb1. I couldn't use my chattering skull but it was marked in my trophies section that I have gotten it , after I sold it it's still marked twords the trophy though so I guess I never had to "use" it

go report this in the known bugs post so theyll fix it
http://forums.elderscrollsonline.com/en/discussion/173858