What do you recommend to be done when an error is found in a pack as it is opened for an operation?

It depends on the type of error. If they put two scalpels in there instead of one but the sterility of the contents is intact, then I recommend you express whatever feelings it gives you in a healthy manner and tell the surgeon about the issue. If sterility is compromised, do not use the pack. Do not touch anything else until you have properly changed sterile gloves after touching the pack. Alert the nurse in charge of documenting the instrument count of your decision.