There is a small grain of flesh inside the navel, if this small grain of flesh protrudes outside the skin are some exogenous flesh flab, usually are benign things, if there is no obvious increase or swelling, pain, generally do not need special treatment, if the swelling is faster can consider surgery to remove. The other condition, if not protruding outside the skin but under the skin, is most commonly sebaceous cysts, which are blocked sebaceous glands inside the skin of the stomach and thus form a chronic inflammation, which over time will soon form a layer of envelope, wrapping some powdered inflammatory material inside, this condition can be diagnosed through ultrasound. If you eat some easy to fire food or stay up late, there may be local swelling, pain, to solve the fundamental problem or should be surgically removed.