The former Blossom star and current Big Bang Theory actress was driving her white Volvo when she collided with another vehicle, which was carrying three tourists from Chile.
TMZ.com first reported that Bialik was nursing a serious injury, and a source adds, "Her finger was almost completely severed... It was just hanging there."
L.A. Police Department Sgt. Monte Houze has now confirmed the actress injured her digit and was hospitalised, telling People.com, "From what I was told, there was a lot of blood at the scene. (Bialik suffered) a severe injury to her left thumb."
Bialik's husband Michael Stone took to Twitter.com shortly after the accident to update fans on the actress' condition.
He wrote on his wife's page, "(husband typing) In pain but will keep all my fingers."