After you have your nose pierced it takes between 4 to 6 months for the nose piercing to heal up fully.
So if you have a nose piercing and want to change the nose ring you need to wait a minimum of 4 months before removing your current nose ring or changing it because it can tear the nose piercing and cause infection.
If you need too or want to change the nose ring you have now after the nose piercing before 4 months you should go to the nose piercing place and have them change the nose ring out for you.
That way you don't risk infection or tearing of the nose piercing area.
If you do get a nose piercing infection you can use soap to clean it and use some apple cider vinegar or hydrogen peroxide to clean the nose piercing area.