Left side leg got swollen. I do now!

My dad is having fever from last 15days, and he was hospitalised due to this from last Saturday. But suddenly yesterday we noticed his left side leg started to swollen, and today it's become huge.. now we consult one doctor and he has no idea about the root cause of this. He just made a little cut at the leg up of the knee, and pull some blood, it was black and some clotted blood. He is guessing it's might be happen due to some injury, and he is telling he will observe it for today, and if the swollen didn't resolve till tomorrow then he will operate on it, and in between that he will do a ultrasonography and x-ray on that leg. He told that my dad's leg is in dangerous condition and can't guarantee about leg. It might need to cut. Plz suggest what should I do now