By Naja Rayne
Updated May 18, 2016 at 05:04 PM EDT

Child star Dustin Diamond got candid in a recent sit-down with his former Saved by the Bell costar Mario Lopez.

In the interview for Extra – his first since being released from jail after being found guilty of disorderly conduct and carrying a concealed weapon – Diamond, 39, opened up about the incident that resulted in his time behind bars.

Revealing that he and his fiancée Amanda Schutz were out enjoying Christmas at a bar in Wisconsin, Diamond shared that at some point in the night a group approached them asking for photos before an altercation ensued.

Diamond says a girl then “sucker punched” his fiancée: “She leaned back to me and her face was covered in blood,” he explains, adding that a man then grabbed Shutz by the hair. “I opened my pocket knife and said, ‘Let my wife go immediately,’ which worked.”

Diamond continued, clarifying that he didn’t actually stab someone in the altercation so much as his opponent “nicked his arm on the top of [the knife] when he grabbed Diamond’s throat from behind.

“It was a Band-Aid, the most expensive Band-Aid I’ve ever bought,” he told Lopez.

In June of last year, Diamond was sentenced to four months in jail for the brawl, along with 15 months of probation.

“It’ll be a total of 120 overnights,” his attorney Thomas Alberti told PEOPLE at the time. “He has to report on Sunday at 6:30 p.m., and then he’ll be out Monday morning to pursue work, and then he’ll report back.”

Talking about his three months in jail (a month less, for working as a janitor), Diamond said: “It’s pretty daunting, it’s pretty scary going into that environment. I found that as long as you follow the rules and stay with the system, it works. You can get in and out unscathed.”

Diamond’s full interview with Extra airs on Wednesday and Thursday.