Umbilical piercings or cysts: The presence of bumps near the belly button that have been there for a year, occasionally tender, suggests a possible complication from an umbilical piercing or a benign cyst formation, which are common in this area.

Sebaceous cysts: These are benign, closed capsules or sac-like structures found under the skin, which can become tender if infected or inflamed.
Lipomas: Benign tumors composed of fat tissue, which can present as soft, movable bumps under the skin.
Dermoid cysts: A type of cyst that can contain skin, hair, and other tissue, which may become inflamed or infected, causing tenderness.
Folliculitis or infected hair follicles: Inflammation of the hair follicles, which can cause bumps and tenderness, especially if the area is shaved or irritated.

Omphalitis: An infection of the umbilicus, which can be serious and requires prompt treatment. Although less common, it's crucial not to miss due to potential complications.
Metastatic disease: Rarely, bumps near the belly button could be a sign of metastasis from another primary cancer. This is unlikely but critical to consider due to its severe implications.
Desmoid tumors: Rare, benign but locally aggressive tumors that can occur in the abdominal wall, including near the umbilicus.

Pilomatricoma: A rare, benign skin tumor that arises from the hair follicle matrix, which can present as a firm, sometimes tender nodule.
Umbilical endometriosis: A rare condition where endometrial tissue grows in the umbilical area, which can cause cyclical pain and bleeding.
Umbilical granuloma: A small area of inflamed tissue that can develop near the belly button, often as a result of irritation or minor injury.