The boy's father took a picture of his son after the attack that shows his cheek is swollen.
Police say the woman's grandson and the boy got into a fight Tuesday.
It all happened at Fairbu Road and Argus Circle.
Police say that grandmother climbed on the bus and punched a 10-year old boy because she thought he had bullied her grandson.

A child's father took this photo of him after a woman allegedly hit him on the school bus.
The boy's father said he could not believe what happened to his little boy.
”The world is just getting crazy man, Jason Stephens Sr. said. ”I would just want to know what would even give her the audacity to just go on the bus and hit my child just for no reason, you know.
According to the police report, Claudette Peters had a reason she went on board bus number 684 and attacked Jason Jr.
The report states Peters went on the bus to talk to the driver about how she believes Jason attacked her grandson the day before. When she did, the report says, she spotted Jason and attacked him. The bus driver pulled Peters off and called police. They arrested Peters and charged her with battery.
Jason went on to school, but then his mother took him to Grady Hospital to get him checked out.
His father said the swelling had gone down by the time he left school to go to the hospital.
The little boy checked out fine and is back home with his mom.