Tell me about the mistake you made and how you have corrected it.

Making mistake is ok but accepting your mistakes and corrrecting them is a good thing and same interviewer is trying to see that do you accept your mistakes and how youcorrect it.  So same you need to share you mistake but not big one and how you have corrected it.
Some steps to correct you mistakes are :
* Identify your mistake
* Take responsibility
* Think of past solutions
* Consider your options
* Formulate a back up plan
* Prevent future mistakes
* Apologize for you mistakes
* Commit to positive change