OK I found it online thanks to the very helpful advice, Hospital Station (Sector General #1) and Mind Changer (Sector General #11) by James White:
In the course of practicing deep-space medicine, that staff has seen more than its share of challenges--from plagues caused by cafeteria food, to cafeteria food that resembles alien species. But now they are facing a disquieting new development: the terrifying Chief Psychologist, Dr. O'Mara, has been promoted to head of the hospital.
Worse, he's been given the job on a temporary basis, for just as long as it takes to train his own replacement. After that, he is up for mandatory retirement. Nobody at Sector General can begin to imagine what they'll do without him--assuming they last long enough to find out.
From the wiki entry for O'Mara:
He originally joined the construction crew that built the gigantic medical facility in deep space. A large man with an imposing physique, his mental capacities and scientific background were constantly underestimated by his superiors. When two Hudlarian construction workers were killed, he was charged with caring for their infant child until it could be moved permanently. After some trouble with the strange alien creature, he read up on its species and quickly learned to take care of its basic needs. After a Hudlarian doctor arrived and took over (noting that the human caretaker had spoiled the baby rotten) O'Mara was offered a chance to join the Monitor Corps and become a psychologist at Sector General.