A groin lump is swelling in the groin that may be caused by conditions such as allergies, cancer, hernia or injury, according to MedlinePlus. Other causes of groin swelling include infection, swollen lymph glands and sexually transmitted diseases.
An individual who has swelling in the groin that lasts for more than three weeks should see a doctor for an exam, explains MedlinePlus. The doctor may visually examine the groin and may perform a pelvic or genital exam. Blood tests, scans or biopsies, may be performed to determine the cause of the swelling. The course of treatment depends on what is found during the diagnosis.