Jason Kelce was back on the ESPN set on Monday, but it wasn’t business as usual for the retired NFL star … who opened up Monday Night Countdown with an apology for his actions.

“I think everybody’s seen on social media everything that took place this week,” the 36-year-old said at the top of the show from Arrowhead Stadium.

“Listen, I’m not happy with anything that took place. I’m not proud of it. In a heated moment, I chose to greet hate with hate and I just don’t think that’s a productive thing. I really don’t.”

Of course, Kelce got into it with a “fan” in Happy Valley at the Penn State vs. Ohio State football game on Saturday … where the Eagles great used a homophobic slur three times, after Travis was called the disparaging term.

Although Kelce clearly wants to move on … it’s not all in the rearview mirror. We’re told police at Penn State have launched an investigation.