I think Mr. Gold is keeping the dagger very safely hidden as I’m guessing he sees it as a sadly dangerous and powerful object since only he REALLY knows the ramifications of the dagger’s curse. I think he views it as an “I wouldn’t wish it on my worst enemy” kind of an object, knowing that Regina would probably “think” she would want to get her hands on it – just like he did. I think he wants to protect the dagger from other people and other people from the dagger, if that makes sense. So I don’t think Regina knows about the dagger. I do think at some point the dagger is going to come into play as part of breaking the curse and I think that it is going to involve Mr. Gold sacrificing himself.