A 12-year-old boy was stabbed in the back while arguing with another child at a Bronx Taco Bell Thursday afternoon, cops said.

The boy was stabbed around 1 p.m. inside the restaurant on Southern Boulevard, cops said.

Emergency medical services took the victim to Harlem Hospital in stable condition with a wound to his lower left back. 

The suspect fled into the Simpson Street subway station.

Police believe the suspect and victim might go to the same school, a police source said.