Access to parts of the record is limited to what is the minimum necessary to perform your role/task. You were working on something assigned by the employer but unless you were assisted with your task by looking at the ED record, your employer would likely say that you shouldn't have. As an illustration, say a Registration employee is tasked with reviewing whether or not ___X___ Registration function was performed on all admitted patients, such as, say, signing Admission Consent. Should they be reading the ED record? No.
Most places I've been, they applied the "minimum necessary" guideline to employees.
Minimum Necessary Requirement | HHS.gov
Get in the habit of asking yourself WHY you need to access the area of the chart you're about to access. If it's for personal interest - - well, that violates the spirit of the law, right? Do it at your own peril.
I think you should say nothing and NEVER do it again.