Brandon Nimmo had Mets fans smiling on their way out of Citi Field Thursday night, but he left the ballpark sporting the biggest grin of anyone.

The 23-year-old has been a bundle of pure joy since arriving to the big club this week, reveling in his first experience at the major-league level while showing some of the skills that made him such a highly touted prospect.

“It’s surreal, this is something I’ve worked for my whole life, so I’m just trying to enjoy this whole experience and soak it all in,” Nimmo said. “No matter what it is, I’m just trying to remember it and put it in the memory banks.”

The Mets selected Nimmo with the 13th pick in the 2011 draft, choosing the outfielder over future All-Star pitchers Jose Fernandez of the Marlins and Sonny Gray of the A’s. Nimmo remembers that day fondly, but getting to Citi Field tops it.

“It’s quite an honor to get drafted, but there’s a select few who become Major League Baseball players,” Nimmo said.

He spent more than five seasons in the minors before getting his call.

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“Everybody kind of thinks, ‘Hey, I’ll just go from this level to this level to this level, to Double-A and then let’s just skip Triple-A and go straight to the bigs,’ ” Nimmo said. “It’s just a different personalized path for everybody. For some it is that, for other people you learn and adjust at each level.

“I think after the first year, I kind of realized, OK, I’m not really in too much control of this.”

With Nimmo still developing last season, the Mets passed on bringing up the Wyoming native, instead promoting 2014 first-rounder Michael Conforto to provide a spark. Seeing someone with three less years of service time promoted might have bothered some, but Nimmo wasn’t disheartened.

“I played with the guy and he’s an amazing hitter and there’s guys that are those pure natural hitters and he had it figured out real quick,” Nimmo said. “He was doing amazing and he was doing great and I really wasn’t, so I didn’t feel like I was being deprived of anything at all.”

Nimmo, who hit .276 with 89 doubles and 30 home runs in the minors, said he was sorry to see Conforto sent down and that the pair exchanged text messages when Nimmo was promoted.

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Now that he has his own shot, Nimmo has been quick to impress the Mets’ decision-makers.

“I think Brandon’s handled it pretty well,” said general manager Sandy Alderson. “He went into a situation, big series in Washington and acquitted himself well and to this point he’s taken advantage of the opportunity, and it’s fortunate that he has because we’re short.”

Manager Terry Collins was impressed with Nimmo’s composure against Washington’s Max Scherzer on Wednesday night and placed him in the leadoff spot Thursday night against the NL-leading Chicago Cubs.

Nimmo showed a bit of what the Mets have been hoping to see. After falling behind 1-2 against Joel Peralta with two runners on in the sixth inning, Nimmo battled back to a full count. On the ninth pitch of the at-bat, he lined a 92-mph fastball to center, driving in the Mets’ second run of the game and advancing to second base on the throw. It was his first RBI in the big leagues.

He scored the winning run when Javier Baez threw the ball away trying to stop Nimmo from moving to third on a grounder by the next batter.

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“A tremendous at-bat against Peralta, who can be really, really tough with the split,” Collins said. “He fouled off some good pitches and finally found something he can handle, but I was very impressed with how he did it.”

With remnants of a shaving cream pie still on his face and the Mets’ celebratory title belt in the locker behind him, Nimmo had another massive grin on his face as he walked reporters through his big at-bat.

“I was just trying to keep things simple, I went over those first two splitters so from that point on, really just trying to be short and get the barrel on the ball somehow,” Nimmo said.

“To be able to come through and help the team win when, you always need it but it felt like [Thursday night] was really, really big. To be able to help the team somehow and come up here, it feels good to contribute.”

And the Mets need contributions in every way.

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“He’s brought quite a bit of energy and is an excitable guy,” Collins said, “and we need some energy right now.”