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.
I hope it helps.