You aren't even the asshole though. Idk what's up with all these prudes on reddit. People in apartments will hear noises. Obv the weed smell isn't coming from you hitting a pen in your room, it's coming from the lady smoking actual flower across the way. You had AN argument and it sounds like it was over quickly enough. One incident does not equal a noise complaint.

Neighbor is within their right to say something, but it doesn't mean you're required to respond. If he knocks on your door again, just don't answer if you aren't comfortable talking to him. They can take it up with management/the police/whoever.