My Father Has A Blood Clot In His Upper Thigh

My Father has a blood clot in his upper thigh and was treated at the hospital. He was sent home after an overnight visit with warforin (sp?) And shots that he must give himself for the clotting. This was on Sunday. This morning his calf muscle started bothering him when he stands or walks. Sitting still, it doesn't bother him. Is this something he should be concerned about? Oh, same leg is involved.