You can do it a couple of ways. I have a rock in my mod that leads to a secret lair for example.
There's a script code - and I'm not 100% sure what it is off the top of my head but it's something like "SetItemIsInteractable(ITEM_Item, Bool);"
You could also just populate the OnUse field in the sidebar with something, then reload the level. Either way should work.
