The most common cause for a black dot to appear on the inside of a person's cheek is an amalgam tattoo, according to simplestepsdental.com. This usually happens after a visit to the dentist for a filling. A small piece of amalgam filling gets embedded in the cheek or gum, and it looks like a small tattoo.
Although amalgam tattoos are the most common reason for a black dot on the inside of a person's cheek, in some cases, the dot could be precancerous, non-cancerous or just a blood vessel. If the spot grows larger or changes color, an individual should visit his or her dentist to have it checked out.