"It's good to be here," he told "NewsHour" co-host Judy Woodruff. "It's good to be anywhere. It's good to be alive."
O'Brien has continued to work on stories for the "NewsHour," including reports on Japan's crippled Fukushima Daiichi nuclear plant, since a seemingly minor injury put his life in sudden jeopardy. His short "NewsHour" interview allowed him to follow up on the ordeal he first disclosed on his blog on Feb. 25.
Looking healthy, even cheerful, in a dark suit and black tie, O'Brien noted that the life of a globe-trotting correspondent is risky in many obvious ways.
"But sometimes, it's the heavy case filled with gear that you need to be careful of," he said, referring to the Feb. 12 blow to his arm by a falling suitcase as he was wrapping up a solo reporting trip to the Philippines after being in Japan.
What began as a bruise became increasingly discolored and painful, he said. When he began to feel numbness in his hand, he sought medical attention on Feb. 14.
He was diagnosed with "acute compartment syndrome," a condition where blocked blood flow in an enclosed space in the body can have life-threatening consequences.
Before his emergency surgery to relieve the pressure, O'Brien said he was warned that amputation was a possible outcome.
"When I woke up," he recalled, "I thought I felt my arm.
Phantom limb pain continues to plague him three weeks later.
It's "incredibly painful," he said. "I feel my hand, in a way, more acutely than I ever did when I had it."
His most successful coping device has been a renewed focus on work, he said, which "got me through a very tough time."
Now, as he begins rehabilitation, he has singled out three priorities: to get back to riding his bike, piloting planes and shooting his own video, as before. He said his doctors told him, "No problem. We have attachments for all of that."
Asked to respond to the concern expressed by his many well-wishers, O'Brien voiced thanks, but assured them, "I'll be OK. I can figure this out. It's surmountable."
The former CNN science and space correspondent covers science for "NewsHour" and is a correspondent for public TV's documentary series "Frontline" and the National Science Foundation's Science Nation online magazine.
His concluding report on the Fukushima plant is scheduled to air on Tuesday's "NewsHour."