How do you know when your belly button piercing is healed enough to change the ring?

Wait at least 2-3 months. If its ready, there wont be any swelling or tenderness. It may be red if you hit it or something like that. I dont change out any of my piercings until I can poke it and lightly tug on the jewelry without it hurting. If you aren't sure, you can always just have your piercer look at it :)