Trent Reznor tried to play it cool.

Yet the Nine Inch Nails front man just had to push pause on that endeavor after some mysterious water dripped onto his head while he was performing “Sin” on Wednesday night at Oakland Arena.

“That’s the first time that’s happened in my life,” the alt-rock icon remarked. “Is there a toilet up there or something?”

Reznor then regrouped himself and went back to the business at hand.

“OK, it’s back to being cool,” said the vocalist-guitarist-keyboardist.

And that he was — as cool as during the band’s ’90s commercial prime — as Nine Inch Nails kicked off the North American leg of its “Peel It Back” world tour in triumphant fashion before a sold-out crowd of some 14,500 fans.

Besides that little watery mishap — which has been reported as moisture dripping from an overhead fog machine — Nine Inch Nails was pretty much unstoppable as it ran through 20 sterling numbers in just over 90 minutes.

Following an opening set from electronic music act Boys Noize, Reznor took the stage alone right at 9 p.m., softly singing and playing keyboards on the 2005 “With Teeth” gem “Right Where It Belongs” from a secondary stage erected at the back of the general admission “pit” area.

He stayed the course, at least initially, with “Ruiner” — from the landmark “The Downward Spiral” album of 1994 — before his band members slowly began to join him on this “B” stage, collectively pushing the music to greater heights and volume as they rolled into the anthemic “Piggy (Nothing Can Stop Me Now).”

The action then moved over to the big main stage, where Reznor and company — keyboardist Atticus Ross, guitarist Robin Finck, bassist Alessandro Cortini and drummer Josh Freese — powered through a six-song segment, bookended by “Wish” and “Gave Up” (both from the 1992 EP “Broken.”)

In between, the industrial rock outfit focused much of its attention on “The Downward Spiral,” performing three sensational numbers — “March of the Pigs,” “Heresy” and “Reptile” — from that quadruple-platinum-selling offering.

The whole band sounded terrific, including Reznor, who remains as passionate and focused as ever on the microphone as he carves out his words with a kind of unsettling anguish that resonates with millions of listeners.

Yet Freese — who recently returned to the band after a stint with the Foo Fighters — might have delivered the most impressive showing of the night, especially given the circumstances.

“This (expletive) rehearsed with us one time,” Reznor remarked with awe about Freese’s pretty much flawless first tour stop back with the band.

As the final notes of “Gave Up” reached the rafters, Reznor moved back to the B stage for a four-song EDM-focused segment with Boys Noize (aka Alexander Ridha) that featured “Vessel,” the (overall) tour debut of “As Alive as You Need Me to Be,” “Came Back Haunted” and, of course, the mysterious water dropping on his head during “Sin.”

The Pennsylvania native then rejoined his Nine Inch Nails mates back on the main stage, where they would remain for the remainder of the concert.

This segment opened with a really nice take on “Somewhat Damaged” — the sole offering of the night from the sometimes-overlooked double-disc “The Fragile” from 1999 — and then moved right into “Less Than” from the 2017 EP “Add Violence.”

The group then ventured into greatest hits territory, where it would pretty much remain for the rest of the show, as Reznor and his fellow rockers hit the crowd with the iconic alt-rock anthem “Closer.” The set closed with three consecutive A-list offerings — “The Hand That Feeds,” “Head Like a Hole” and “Hurt.”

It was a great start to the North American tour, one that should have fans living in other parts of the U.S. and Canada counting down the days until NIN hits their towns.

Nine Inch Nails Wednesday set list:

1. “Right Where It Belongs”

2. “Ruiner”

3. “Piggy (Nothing Can Stop Me Now)”

4. “Wish”

5. “March of the Pigs”

6. “Reptile”

7. “Heresy”

8. “Copy of A”

9. “Gave Up”

10. “Vessel”

11. “As Alive as You Need Me to Be”

12. “Sin”

13. “Came Back Haunted”

14. “Somewhat Damaged”

15. “Less Than”

16. “Closer”

17. “The Perfect Drug”

18. “The Hand That Feeds”

19. “Head Like a Hole”

20. “Hurt”

*Based on our notes and information from setlist.fm.