Baldwin Luigi Singh, a nursing student, said he wanted to protect his younger brother from the bully who had threatened to beat up his brother.
But the suspect, detained by police along with another of his mate being suspect, has accused Singh of hitting his younger brother. Singh denied the allegation.
Singh's 13-year-old brother has not been named for being a minor. Police have confirmed the incident.
Singh's and the suspect's younger brothers first got into a fight two years ago over a football game, according to The Straits Times.
Suspect has been detained by the police for further investigation
The youngsters feud worsened this year when both entered the same school. Singh's younger brother alleges that the suspect's younger brother and friends had "hit my head and pulled my turban twice in January".
Things went downhill last Friday when Singh decided to go with a classmate to meet the suspects at a playground.
Singh claims the suspect walked towards him with a knife hidden in a plastic bag and stabbed him in the chest.
Singh, his brother and friend ran away from the scene. He went to a family clinic and sought medical help while waiting for an ambulance.
Police have established this case as voluntarily causing hurt by dangerous weapons. Further investigations are on.