The boy's uncle, Mr Chen, told the news website that the family had to pay more than 75,000 yuan ($16,600) for his nephew's medical bills, and that the company had given them just 3000 yuan in compensation.
"But when the accident happened, they told us they would cover all the medical expenses," he was quoted as saying.
It was not clear whether any further action would be taken against the property management firm.
A window fell from another building in the residential community just weeks ago.
No one was injured on that occasion, which was blamed on workers failing to follow safety procedures when they installed an air conditioner on the outside of the building.
There are regular cases of people being injured by objects falling from high-rise buildings in China.
According to Chinese law, if no one is found responsible, all users of the building where an object fell from - except for those who can prove they were not involved - must compensate the victim.
In 2016, a man riding an electric bike was killed when he was struck on the head by a brick falling from a high-rise building in Wuhu, Anhui province, Xinan Evening News reported.
A year later, a local court ordered 133 people from 81 households in the building, along with the property management firm, to pay compensation of 500,000 yuan to the victim's family.
In Guangzhou last year, a woman was seriously injured after she was hit by a dog that fell out of a building.
The dog survived and ran off, but the woman spent 20 days in intensive care recovering from neck injuries. Police were unable to track down the dog's owner.
- South China Morning Post
