From your terminology, one assumes this took place in the USA. If so file an ASRS right away, and in the REPORTER section, put something like 'Pilot Under Training'
Also ask if the instructor has filed one, but whether or not they have, do your own.
the form is here
https://asrs.arc.nasa.gov/report/cav...rmType=general
What others have said above about PIC etc is true, but the FAA is very different to the CAA. We are discussing a pilot deviation report being placed on your FAA history , not a prosecution. Yes, the instructor is likely going to get in trouble/may also get a deviation , but regardless there is a good chance of getting a pilot deviation filed against you. You are instrument rated and a commercial student, the FAA will consider you to be a skilled pilot who should know better, so get that ASRS report straight in and be humble !