Worked with F1 I-20 without getting CPT approved

Hi, I have worked with a F1 I-20 without getting my CPT approved. I’m not aware that CPT is not approved so I finished the semester with 7 credits only and started working with that F1 I-20 only. This is my second masters after my STEM OPT got expired I moved to other university and they are saying it’s an issue working without CPT got approved. What can I do at this situation. Please help me with this.

You cannot work without any authorization from DSO and same approved by DSO. You need CPT or OPT to work.
Talk to DSO and see what are your options. They may ask you to exit and re-enter the country to avoid your violation of status. Talk to an attorney on this as well and plan ahead.