My thoughts
These are just my thoughts and is not a legal or any other form of advise.
1. At the time of application, on the day you signed and dated the 485 application you did not have a violation. So you are not hiding any material information - So, I think, you are okay. You do not need to volunteer any information.
2. At anytime after your violation the question is asked, you should not hide the facts - so, be it an interview with INS or any other application. You may also have to prove that the violation occured after the disclosure on the application.
Again, these are barely my views and not any legal advise. Please contact an attorney for any clarification.