He already told you the ball is back at HR. You don't want to look too eager by forcing him to revisit what he has already finished with. You would be telling him that you have doubt about your performance at the interview. What do you want him to think about his judgment?
Your attitude should be: I did my best at that moment. I'm fully responsible for my part of that exchange, good and bad. Let the chips fall wherever they may. Your (future) boss will appreciate the way you shoulder the burden.
It takes time for HR to put everything together, especially now.
(The 2nd interview was scheduled the next day was because the first interviewer was told by the 2nd interviewer to go ahead.)
