A hospital spokeswoman said the nurse was "released physically unharmed" and police said no threats were made about the safety of the medic.
The hospital remained open while some ambulances were diverted elsewhere.
The spokeswoman added: "Some patients who were close to the incident were moved for their safety and non-urgent ambulances were diverted to other hospitals during the incident.
"Our staff kept calm and responded magnificently to a very difficult situation.
"Our priority now is to return the ward to normal and ensure the nurse involved and other staff and patients close to the incident receive the support they need."
A West Midlands Police spokesman said no weapons were found.