This lump can be a hematoma, swollen lymph node in response to an infection, abscess or an inguinal hernia. It is a result of a weakness, tear, gap or opening in the muscle wall of the lower abdomen or groin through which the contents of the abdomen, such as intestine, may protrude through the muscle creating localized pain, pressure and a feeling of heaviness.
I suggest you to get this lump examined from a surgeon to confirm the diagnosis. The best test for confirmation of this lump is a FNAB (fine needle aspiration biopsy) of the lump which should be got done after consulting a physician. FNAB is aspiration of the material of the glands which is done by a fine gauge needle (22 or 25 gauge) and a syringe. Then the material is looked under the microscope to confirm the diagnosis.
I hope it helps. Take care and regards