I have a small painful lump in my groin
A femoral hernia sits lower in the groin than an inguinal hernia. They tend to be smaller and are often difficult to reduce (ie they tend not to disappear when lying down). They form as the ligaments around the femoral canal start to weaken and are thus seen more commonly in older patients, particularly women who have had several pregnancies.
Because the neck of the hernia is tighter than most inguinal hernias they are at greater risk of strangulation and thus in most cases should be surgically repaired.