Hey johnnyquest61,
Thank you for posting your concerns here. I understand how frustrating it may be to unknowingly join a modded lobby and have your stats altered. The best thing you can do is to immediately leave the lobby and report any players you suspect of cheating via in-game report tool here. We are not able to reset stats at this time, but we will update you once/if we add that feature. If you have not violated the security enforcement, you should be okay. We are unable to say 100% as these are matters our security team handles.
Best,
^MC
ATVI Support