A generous teenager from Westchester recently completed a project to enhance a nearby veterans hall just in time for Memorial Day. This accomplishment came after a sudden accident and a challenging period of recovery had delayed his efforts for several months.

Joseph Mana, 18, was nearly done fixing up the Veterans of Foreign Wars hall in Yorktown Heights, installing planter boxes, pressure washing the building and refinishing a bench, for an Eagle Scout project in October when he took a break to return to school, he and his father told The Post.

“It was supposed to be done in time for Veterans Day — but then tragedy struck,” his dad, Ed Mana, said.

The teen, who was active in Boy Scouts troop 173, was playing touch football in fourth period gym class when another student accidentally slammed into his left leg from the side as he leaned back on it, Mana said.

The impact and strange angle dislocated his knee and damaged a main artery behind it.

“I was in a lot of pain and shock,” Mana said. “The top of my knee was indented down at an angle.”

He was rushed to an emergency room, where doctors explained he needed surgery immediately to fix the artery.

“After they popped it back into place, they said it could be something wrong with the vascular side,” Mana said.

For the next four months, the teen was forced to remain hospitalized while he recovered from three surgeries — including to repair the artery, remove pins from his ACL and fix a tendon.

Ed Mana, 52, said it was hard to check his son into Blythedale Children’s hospital in Valhalla knowing he’d likely be there for months.

“When you have to leave [your kid] there, it’s like you’re leaving someone in jail. There were tears,” he said.

As the months passed, the teenager celebrated Halloween, New Years ‘Day and his 18th birthday at the hospital.

“I was upset and annoyed I couldn’t see [my friends],” Joseph Mana said.

He even applied to colleges while on painkillers and confined to the medical center.

“I told him if you don’t get in, you should write the college a letter later and say, ‘I was high but not for the normal reasons,’”  Ed Mana said.

Finally, in March the teen was released and advised to do physical therapy twice a week and to wear a knee brace for the next year and a half.

Over the weekend, he returned to complete the vets project, which will also include a flag box, and will be unveiled in a ceremony after the town’s Memorial Day parade Monday. Mana is expected to give a short speech.

“Vets deserve this because they fought for our country, so we should spend our time helping them too,” he said.

Since his accident, Mana has been accepted to SUNY Polytechnic Institute, where he plans to study computer science.