A belly button piercing can take from six months to a year to fully close and heal, depending on how long the piercing was in place. A naval piercing can take longer to heal if there has been any kind of infection, scar tissue build-up or tearing of the hole.
In order to dependably heal a piercing, be sure to apply alcohol to the piercing to prevent infection and irritation. Do not use antibiotic ointment as it can trap moisture inside the piercing, causing infections and slowing the healing process. If there is any swelling or redness, see a doctor.