A nodule felt on the upper left side of the navel may be related to sebaceous cysts, boils, lipomas, abdominal wall fibromas and other causes. 1. Sebaceous cyst: A sebaceous cyst is formed when the sebaceous gland secretion accumulates under the skin due to the blockage of the sebaceous gland opening on the upper left side of the navel. 2. Boils: If the single follicular opening on the upper left side of the navel is infected by bacteria, it can cause a localized inflammatory reaction, resulting in the appearance of a small nodule, which may be accompanied by itching, pain and other symptoms. 3. Lipoma: if there is a lipoma under the skin of the upper left side of the navel, a nodule protruding from the surface of the skin may appear. 3. Abdominal wall fibroma: if there is a fibroma growing on the left upper side of the navel protruding from the skin surface, it may appear as a nodule. It is suggested that if you feel a nodule on the left side of the navel, it may be caused by malignant tumors in the abdominal cavity. Therefore, you should go to the hospital in time, complete the examination, and be treated accordingly after a clear diagnosis.