Appendicitis: This is a common condition that presents with pain, often starting near the belly button and then moving to the lower right abdomen, and can be associated with a palpable lump if an appendicular mass forms. The pain is usually severe and accompanied by other symptoms like fever and nausea.

Inguinal Hernia: A hernia in the groin area can cause a painful lump, especially if it becomes incarcerated or strangulated. The lump is usually more prominent with coughing or straining.
Ovarian Cyst (in females): Ovarian cysts can cause abdominal pain and a palpable mass. If the cyst ruptures or torsion occurs, the pain can become severe.
Diverticulitis: Inflammation of a diverticulum in the colon can cause pain, usually on the left side but can occur on the right, and may be associated with a palpable mass if an abscess forms.

Ectopic Pregnancy (in females): Although less common, an ectopic pregnancy can present with abdominal pain and a mass. It is a medical emergency due to the risk of rupture and severe bleeding.
Intestinal Obstruction: Obstruction of the intestine can cause severe abdominal pain, vomiting, and a palpable mass if a closed-loop obstruction occurs. It requires prompt surgical intervention.
Ruptured Aneurysm (e.g., abdominal aortic aneurysm): While less common, a ruptured aneurysm can present with severe abdominal pain and a palpable mass. It is a life-threatening condition requiring immediate medical attention.

Lymphoma: Abdominal lymphoma can cause pain and a palpable mass due to lymph node enlargement. It is less common and usually diagnosed after other more frequent causes have been ruled out.
Soft Tissue Sarcoma: A rare type of cancer that can occur in the abdominal wall, presenting as a painful lump. Diagnosis often requires imaging and biopsy.
Psoas Abscess: An abscess in the psoas muscle can cause lower abdominal or back pain and a palpable mass. It is relatively rare and often associated with underlying conditions like osteomyelitis or spinal infection.