Answer honestly because anyone who says they’ve never made a mistake is obviously lying or delusional. As unpleasant as it may be to discuss, you must admit to a mistake and explain how you made things right in some detail.
Admit your mistake and take full responsibility for it. Don’t try to blame someone else or spread the blame around, taking only part for yourself. Interviewers don’t want to hear how your teammate gave you bad information and caused your mistake.
Explain in detail how you solved the problem. And be honest about it, no matter how bad you feel your explanation may make you look. The interviewer won’t usually see it that way.
As long as you were able to learn from it, you can admit to most any mistake—within reason. The interviewer is looking to hear that you did learn from it and put parameters in place so it does not happen again. Tell a story that highlights your ability to learn—and learn well enough not to make the same mistake again.