As long as the unregistered gun you have is a legit gun that you own and have gotten legally then there's nothing wrong with having the unregistered gun in your possession.
As of now the law states that it's not illegal to have in your possession an unregistered gun.
Still it would be a good idea to have the gun registered in case something happens that way you can easily prove the gun is yours especially if the gun gets stolen.
But keep the gun locked up at all times when not using the gun and unless the police have a search warrant they cannot and will not know about your unregistered gun.
I have an unregistered gun that was my dad's that he gave to me but I don't take it off my property and I lock it up when not using it.
So I'm not worried about registering the gun.
But other guns that I take with me in my vehicle such as for hunting and protection I have those guns registered to myself.