Failure to cooperate with a criminal investigation can be a misdemeanor and can carry jail time as a consequence. Only the prosecutor knows whether 1) the case against the doctor needs your testimony and 2) you will be prosecuted if you fail to cooperate with the prosecutor.
Simply put, I suggest you honor any subpoena and tell the truth when you are on the witness stand under oath.
If you fail to come to court having been subpoened they can issue a bench warrant for your arrest. I you refuse to answer questions they can hold you in contempt. If you answer questions falsely, and they can prove it, they can charge you with perjury. If you deny that it happened they can charge you with filing a false police report. So yes, you could go to jail.