I don't think your employer (the civil service) will impose any punishment on such an infraction that took place outside of office and work hours, especially when no jail time is involved. People do get involved in fights but they don't necessary lose their jobs. What about the tons of traffic and parking offenders ? If I recall correctly there was a public figure who abused her maid, was fined but still in the employment of a stat board.

The other issue is honesty. Being honest is the best and you did right here. When you start with one lie, you have to cook up more and more lies to cover the earlier ones. At the end of the day, you have to answer to the maker.