I was giving an introductory flight to a friend who I am trying to get interested in obtaining his pilots license. While he had the controls, I was so focused on watching and helping him that I think I busted the bravo. It may have only been for a cpl seconds, as I realized it immediately. But, nonetheless, I still did. What steps should I take with the authorities to acknowledge this mistake?
File an ASRS report with NASA saying what you did wrong and what you should have done differently. If the FAA decides to take certificate action against you, this will be taken as evidence of a constructive mindset, and it provides immunity to certificate action, so long as this was a first offense and was inadvertent. Make sure you keep the submission confirmation number and the identity strip they send you. NASA keeps no record of who submits these reports so you will need to keep this for evidence that you submitted the report if the FAA comes knocking.
Just as importantly, learn from the experience. If you are PIC, anything your passengers do is your fault. You should be at least as vigilant when a passenger has the controls as when you do, and be certain that your proficiency is up to the task of monitoring them without losing situational awareness. It's probably prudent to only give the controls to a passenger when well-removed from busy airspace.
The recommended course of action is to submit a NASA ASRS report (full form here) admitting your mistake and explain the situation. These are non-punitive reports and are a good sign you understand what you did, acknowledge it, accept the responsibility and are working to remediate should the FAA launch an investigation.
Depending on when this happened if you and/or the flight school has not received a phone call about it you may be in the clear but keep in mind they can be slow. Assuming your aircraft had ADSB out they would have known who you were.