There are many different types of personality disorder. The most "common" is borderline personality disorder, one of the criteria is self harm and so many people get misdiagnosed just because they self harm.
These are the different types-
http://en.wikipedia.org/wiki/Persona...ned_in_the_DSM
If you were diagnosed with a PD you could still work as a mental health nurse as long as your symptoms were managed and you got clearance to work from your psychiatrist. Being a mental health nurse is extremely demanding and no matter what you're diagnosed with you will need to be stable before you can do that job.