Legal Question in Medical Malpractice in California

It's a violation of the Health Insurance Portability and Accountability Act. You can file a complaint here:

http://www.hhs.gov/ocr/privacy/hipaa/complaints/index.html

You could also sue the nurse practitioner and his or her employer for a breach of your privacy, but unless the circumstances are unusual (for example, a disclosure of a disease that would cause some people to think poorly of you) then it's not likely there's a great case here.