The star slipped over during the second half of Shakespeare's Timon of Athens at London's National Theatre and he halted the performance when it became clear he was hurt.
Understudy Paul Dodds took over and Beale was admitted to St Thomas' Hospital for treatment.
A spokeswoman for the theatre tells the BBC, "He had his fingers splinted at the hospital. It was his right hand so he has had to slightly amend his performance."
Dodds says of the incident, "I didn't have time to get nervous. It was about an eight-minute turnaround from Simon deciding he couldn't continue to me going on stage to replace him. I think I very quickly became some kind of pragmatist! The audience gave me a tremendous welcome and I just got straight into it. It's probably the only time I'll get to play a Shakespearean character in front of an audience of 1,200."
Beale resumed his role in the play on Thursday night (20Sep12).