Have you spoken to your sponsor? First thing first would be to close all accounts this person has any access to then talk to a lawyer and see if there is anything that can be done.
Have you spoken to your sponsor?
If this has no real effect on your credit or your life it may be best just to let it drop.
Are you wanting to pursue this for revenge or out of need? Resentments are things we need to rid our selfs of, revenge is not a good way to get rid of resentments.