Why are you leaving your current nursing position?
Don't tell the negative things about your previous hospital or organization, saying this will make your impression self-centered or unappreciative. Instead, you can say you are looking to enhance your skills, and you just want to change your work location (region, state anything).
Note: This is the question where you have to be truthful, but you can answer it diplomatically. Almost all the interviewers will get what you are trying to say since it is one of the common nursing interview questions.