You leave it alone and pretend you never saw it.

[ Seriously, Jaune. Your kneecaps will be forfeit if you even touch Nora’s diary. Gently, she relieves him of the rest of the coupons, sets them back in the drawer, and closes it with a soft click. Adding, then, ]

Besides, Nora keeps it very well hidden. Our room at Beacon was a lot smaller than this. [ If he hadn't accidentally stumbled upon her journal then... ]