This video shows you how to use a retainer to hide a tongue piercing. A retainer is usually made of a clear, flexible material that has a silicone feel to it and can be purchased in various styles and sizes for different body piercings. Many people have tongue piercings for a long time without being noticed by those around them.
Try to avoid removing all jewelry from your tongue for any reason, as this can cause the piercing to close very quickly (some people report their tongue piercing closes within minutes or hours of jewelry removal). Retainers are usually inexpensive to purchase and are available from online sellers of body jewelry and body piercing supplies.