A day after making his retirement official, CC Sabathia was back at Yankee Stadium, packing up his things.

“It feels good,” Sabathia told The Post on Tuesday. “It’s time to go.”

The 39-year-old lefty admitted the shoulder injury he suffered during the ALCS in his final pitching appearance helped convince him he had made the right call to end his career.

“I knew it was time,” Sabathia said. “My arm’s messed up. I think I would have had lingering thoughts about coming back [next year] if I didn’t get hurt, especially because we didn’t win the World Series, which was one of the reasons I came back this year. But with my arm feeling the way it feels, I know I can’t do it anymore.”

Because Sabathia’s injury forced him to be replaced on the ALCS roster, he would have had to stay off the World Series roster if the Yankees has advanced. Sabathia said, “I would still have loved to have been there, even if I wasn’t playing,” and he is convinced the Yankees — who were eliminated by the Astros in a dramatic Game 6 on Saturday night — will win another title soon.

“The way we fought to the last at-bat with DJ [LeMahieu] and his home run, that epitomizes what this team was and how tough this team is,” Sabathia said. “The guys showed a lot of toughness. I know this team is gonna win the World Series, with this group of guys. It was just fun to be a part of.”

Sabathia will ease into retirement. He said he’s not sure what he will do now (“We’ll see,“ he said). Surgery to repair his separated shoulder will happen “at some point. I’ve got a couple of vacations to go on first.” Sabathia said he has yet to discuss a potential front office role with the Yankees, which he expressed interest in during the season.

Sabathia said he’s come to grips with how it ended — and doesn’t have any regrets.

“It was emotional when I got home [Sunday] night, but I’m fine with it,” Sabathia said. “To pitch till I can’t pitch anymore, to play in the ALCS in my last year, to pitch in the big leagues for 19 years. It’s a blessing. I can’t complain about anything.

“I’m at peace with the decision and it being final. I don’t think there’s anything else I can do out on the field.”