There are two things here: you being stabbed and you stabbing the person. According to 10,000 Dreams Interpreted being stabbed denotes that disgrace may follow. Stabbing someone denotes baseness of character, and you should strive to cultivate a higher sense of right.
Even though it's bad news for both situations the second can be tricky because it was self-defense. But then again, it's just a book on dreams that I find interesting. I also have a book on superstitions for those who have an interest.