Williams said there was pain and swelling in her ankle and X-rays were an option, but she wanted to leave any decisions about treatment for a few hours.
"I've been injured before," she said. "I've played this tournament with so many injuries and was able to come off pretty on top. So for me it's just another page and a great story to tell the grandkids one day."
Defending champion Victoria Azarenka also advanced, overcoming a wobble in the second set to beat Monica Niculescu 6-1, 6-4 on Rod Laver Arena. Andy Murray won his first match as a Grand Slam champion, beating Robin Haase of the Netherlands in straight sets.
With a packed program on the center court, Williams was playing on the second of the show courts.
The 31-year-old American was leading 4-0 after 19 minutes when she fell awkwardly chasing a ball wide on her forehand side, putting both hands over her face.
She rolled from her back to her hands and knees, where she stayed for several minutes before she was helped to her feet. The 15-time major winner started limping before easing into a walking stride as she made her way to her court-side chair to have her already heavily taped ankle treated and then re-taped.
"I think I was really, really close to panicking because a very similar thing happened to me last year, almost on the same side, the same shot," Williams said. "So I almost panicked, and I thought, I can't do that. I just have to really remain calm and think things through."
Storylines Surviving Round 1
R Serena Williams overcomes an ankle injury to beat Edina Gallovits-Hall 6-0, 6-0.
• Defending champ Victoria Azarenka also wins.