Although I carry a knife all the time, you hafta remember cops dislike them, and you may be blamed for doing something even if it was out of self defense. By law (at least where I live) you are only allowed to use a "deadly weapon" as a last resort, and only when it means life and death for you or someone else. If the cops don't feel you expended all other options first, you, not your attacker/s, will be punished. Also, knowing blade length laws where you are is always a must, because where I live there isn't one, but if I go to Chicago fifty miles south, it's 3.5" or you'll get charged with carrying a deadly weapon and probably some premeditation BS
As for the story, that is pretty cool, you're really lucky, and I'm glad it didn't go to your head, I'm sure a lot of preople would think they're the best ever if this happened to them.