When should I move my son to his crib?

Currently sleeps in a bassinet in our walk in closet. We are on the main floor and his bedroom is upstairs. It makes me nervous having him so far away when he is so little! When do you suggest transitioning him into his own crib? He sleeps 12 hours at night so not like we would be getting up with him during the night. Thanks!

(He’s currently 4 months old)