Sounds like nerve pain. Perhaps a nerve that extends from your abdomen down to your leg was irritated by the trauma of the kidney stones. Did you pass them, did they break them up, or surgically remove them? I would follow up with the doctor who treated you at the hospital to ask him about it. It could also be referred pain from the abdominal area.
Meralgia paresthetica due to pressure. Physiotherapy helps. ok?
My best wishes.