Biting down on your lip or tongue unexpectedly is never fun. You might be chewing just like you normally do, when you suddenly bite down wrong and end up injuring yourself. You may also bite yourself in the course of an accident that presses your teeth against your lips or tongue. Children often accidentally bite their lip or cheek after being anesthetized for dental work. Most times, biting your lip or tongue only results in pain and swelling, and heals fairly quickly. But there are some instances where biting down on your lip or tongue requires emergency medical attention.