This was the doctor with Kid and Father in the Season 3 episode One Day, One Room. He was portrayed by actor George Williams.
House had earlier paid Father to leave the clinic and got upset when he saw them return. The doctor insisted that Kid needed emergency surgery as he had swallowed a kitchen magnet. The doctor insisted that because the magnet was strong, they couldn't use imaging to find it. House grabbed a nearby scalpel and the doctor freaked out when he thought that House was going to cut the Kid. However. House was merely using it to locate the magnet and found it had passed well into his intestines and posed no further danger.