The children were playing with the gun, which was left under the couch by the boyfriend, Charles Sanders, according to the station.
Sergeant Mickey Keaton of the Shelby County Sheriff's Office told the television station that the young girl "wasn't severely hurt, so we're thankful for that."
Keaton suggested the use of gun locks and secure storage to prevent such accidents.
"They're your children," Keaton said. "It's up to you to keep them safe."