A retired FDNY firefighter testified Wednesday that he was so severely injured in a 2015 East Village gas explosion that he now lives in constant agony.

Former Battalion Chief Edward Tierney, who was called to the stand on the 18th anniversary of the 9/11 terror attacks, said that the March 26 blast — which killed two people — changed his life.

“I live in pain,” he said at the manslaughter trial of landlord Maria Hrynenko, contractor Dilber Kukic and unlicensed plumber Athanasios “Jerry” Ioannidis. “I can’t even put a pair of socks on.”

Assistant District Attorney Randolph Clarke Jr. showed jurors photos of Tierney, 67, looking healthy and fit as he fought the fire moments before he suffered the injuries.

“When all the debris started falling I actually got struck two or three times,” he recalled. “I fell down two times and had to be helped up.”

He later fell again, twisting his back and hitting his head.

Despite his injuries, Tierney remained on the scene until late into the night when he finally went to Beth Israel hospital for treatment.

Soon after, he endured two knee replacements, a shoulder replacement, a hip replacement, back surgery and other procedures.

“It ended my firefighter career,” said Tierney. “It was a complete life changer for me. Complete. I’m not the person I was after that. Not even close.”

He told jurors he tries to walk and lift light weights but struggles daily with severe pain and mobility limitations.

“I can’t even cut my toenails. Yesterday I had my daughter do it,” he told jurors in Manhattan Supreme Court. “I used to love to swim. It’s too much. It’s too much pain.”

Then came more bad news. In 2017, while recovering from the surgeries, Tierney was diagnosed with a rare blood cancer, for which he’s currently being treated. The ailment likely stemmed from exposure to toxins at Ground Zero following the 9/11 attacks.

Tierney spent Wednesday morning at his old Harlem firehouse, Engine 59/Ladder 30, attending a 9/11 memorial service.

“It’s extremely sad, especially when I see the children,” he said of the tragic day. “We lost a lot of senior members.”

Prosecutors say that the defendants, motivated by greed, installed a series of pipes and valves to illegally divert gas from 119 Second Ave. to the adjoining building, 121 Second Ave., both owned by Hrynenko.

The dangerous rig eventually led to a gas leak and explosion that showered the streets with debris and leveled three historic buildings.

They face manslaughter, criminally negligent homicide assault and other charges.

Tierney has a pending civil lawsuit against Andrick Management, LLC, the construction company overseeing apartment renovations at 121 Second Ave.

The suit alleges that the company’s negligence and recklessness caused the blast.