The 35-year-old country singer spoke to Vulture about how most of the injury's effects were more mental than physical.
"I felt like the differences were more in my head than they were in anybody else’s that would listen to the things I was doing," she says of getting back in the studio to record 'Cry Pretty,' her latest album that dropped Sept. 14.
"I had wanted to be in the studio sooner than I was, actually recording these songs, but I had stitches inside my mouth, outside my mouth. It was physically impossible."
Underwood calls her first trip to the studio post-fall "a mind game," and admits to having an internal monologue full of questions and doubts.
"'Do I sound the same? Is my diction the same? Does my mouth move the same as it did before?'” she recalls questioning.
"I would sing something and then look at [my co-producer, David Garcia] and be like, 'Did that all come out clearly?' My m’s and b’s and p’s were kind of the issue. And he was like, 'I thought it sounded great.'”
"Things change just as you get older; your muscles change," she adds. "I kind of expect I’m not always going to sound like I’m 22 coming off of 'American Idol.' Hopefully I get better."
The injury to her face is just one of the setbacks Underwood faced over the last couple of years.
The "Before He Cheats" singer also suffered two miscarriages with her husband, Mike Fisher, before announcing her pregnancy back in August. The pain from those experiences led to more honest and personal lyrics on her latest album.
"It would be completely inevitable," she says of her emotions infiltrating her songs.
"I’d have a terrible day at the doctor’s office and then come into a writing session and be like, 'I’m sorry guys. I might suck today. I just got some bad news.'"
"Things aren’t literal, but I look at a song like 'Low,' and that was my year last year," she shares.
"It was not about a person leaving or anything like that. I listen to that song now, and there’s a good chance I’ll cry, because it was just so personal."
"I kinda needed [music] at the time, just to have something to stay focused on that wasn’t my personal life," she adds.
The personal aspects of her album led her to take "more ownership over what I was doing in my artistry," what she calls "a leap of faith," and credits with being "such a growing experience... as a vocalist."
"It was just trying to move the artistry forward and not do the same things that I’ve always done," Underwood says.
"Like, I literally hold out notes until I start seeing stars. I will pass out some day on stage. It hasn’t happened yet, knock on wood. But it probably is really only a matter of time, because I will push myself until it hurts, which I love [to do]."
"It was just such a great artistic step forward, being able to feel a song and deliver it in a different way," she says.
Back in September, a source told ET how Underwood got through one of "the most challenging years of her life."
"She had big plans for herself and every step of the way she faced roadblocks," the source said at the time.
"... Carrie is a great mother and an amazing performer and wanted 2017 to be her year. She made some big changes in management but dealing with her career, her miscarriages, her fall and losing part of her team was almost more than she could handle."
"She has come a long way and we are all so proud of her," the source added. "She is incredibly strong. She has an incredibly supportive family and leaned on them and her closest friends to get through it all."