Violation class bravo airspace
You're probably fine.  File a ASRS form all the same though.

The feds tend to focus on safety of flight issues or gross violations that indicate general incompetence.  Some guy flying below a B shelf doesn't rise to the level of incompetence (because it's not).  Worst case, you caused a resolution advisory for an airliner which, in the grand scheme, is not a huge deal (for you, legally) if you were following the rules (sounds like you were).

If you get a letter, call an aviation attorney.  I doubt it will come to that though.

Keep on flying.