Get Stamina From Object? Do I need to set up an inventory for this to work?

Another way would be to use data table, it would work with different kind of consumable(mana pot, health pot, etc)

This link shows you how to do something like that with Excel, but you could do it all in game with a custom struct
(Struct Variables in Blueprints | Unreal Engine Documentation)
where you would have the name of the potion, how many points it refunds, etc.