There isn't information about NOS diagnoses because they are not defined disorders. DDNOS simply means that a person has symptoms of dissociation, but doesn't meet the criteria for any of the specific currently recognized dissociative disorders. Another way to think of it is a person could have a Mood Disorder NOS which would mean they have some symptoms of depression and or mania, but what they have is not the same as recognized depressive disorders or bipolar disorder.

Anyone could have an introject without having any mental health disorder at all. People are all different, and you can have a symptom or several symptoms without having a diagnosis, just like you could have a headache without having the flu or any particular disease. The more symptoms that someone has, and the longer they last, and the more problematic they are, the more likely that they will be recognized as one disorder or another, but the bottom line is that whatever you experience is what you experience, and that you get treatment if needed or otherwise learn or are able to live the best life that you can. If a negative introject takes away from your experience of life, it may be helpful to recognize it, understand where it came from and how it affects you, confront it, and replace it with self-talk and boundaries that work better for you.