A left-shoulder injury to Novak Djokovic didn’t prevent him from winning a second-round match in his bid for a second straight U.S. Open title.

But questions about the rest of his Flushing road now linger.

A wincing Djokovic, despite being attended to twice by a trainer, survived his second-round battle against 56th-ranked Argentinian clay-court specialist Juan Ignacio Londero, 6-4, 7-6, 6-1, on Wednesday’s Arthur Ashe Stadium nightcard under the closed roof.

“I’ll probably freeze my arm for 48 hours and not do anything with it,’’ Djokovic said in his on-court interview.

Nearly two hours after the match had ended, Djokovic had not yet showed up to the interview room as he got treatment.

When he finally arrived, Djokovic sounded the alarm.

“The way it has started for me, especially midway through the first set, I didn’t know if I would be able to finish the match,’’ Djokovic said.

Then he added he would get further consultation Thursday on the extent of his injury.

“I’m going to assess this injury [Thursday] even more, further consultations with experts in sports medicine,’’ Djokovic said. “I’m hoping that in two days’ time I will be able to play pain-free, if that is possible.’’

Leading 4-3 in the first set, Djokovic got treated during the changeover by a medical trainer, who gave a deep massage to his shoulder.

Djokovic revealed the injury occurred before the Open began, saying it’s bothered him for “a couple of weeks” — which could explain his loss in this month’s Cincinnati tune-up to Daniil Medvedev.

Djokovic squeezed out the first set against Londero, a journeyman who had never played at the Open. The 26-year-old is enjoying his career year after advancing to the round of 16 at the French Open.

Afterward, the Serbian admitted his shoulder was “definitely affecting’’ his serve and backhand.

“I was definitely tested,’’ Djokovic said. “It’s something carrying for quite a while now. It wasn’t easy playing with the pain. You have to find a way to fight and get some lucky shots.”

Things really looked grim for Djokovic early in the second set. Laboring with his serve, he fell behind two breaks at 3-0. He double-faulted on break point in the first game and matters looked dire. He failed to get o to a drop shot on his next service game to put Londero up 3-0.

Then it all changed. Djokovic shook off the pain and rolled to win five straight games.

“I had some luck in the second set to come back,’’ Djokovic said. “It’s not the first time I’m facing this adversity or challenge. It was definitely a difficult match to play.’’

Londero couldn’t explain it and couldn’t tell how injured Djokovic really was. Speaking in Spanish, Londero said through a translator, “I was playing at 100 percent, then I was playing at 95 percent and I’m facing the best player in the world.’’

Djokovic’s draw isn’t exactly a cakewalk. In the fourth round, he could meet up with stalwart Stan Wawrinka. In the third round he will play the winner of the Dennis Kudla-Dusan Lajovic match.

Djokovic is vying for his fourth Open title, 17th Grand Slam and third major of the year after winning the Australian Open and the Wimbledon classic against Roger Federer.

In his past 11 appearances here, Djokovic has reached at least the semifinals. His shoulder has put that streak in doubt.