The teen was rushed to a local hospital after he cut himself with the large blade and spent two days receiving treatment.
A doctor said he doesn't understand why the teen tried to circumcise himself because he could have been visited by a voluntary circumcision team at home.
Dr Nyasha Masuka, medical director of Matabeleland North Province, confirmed the boy tried to cut off the foreskin of his penis after he was mocked by his friends.
Dr George Mature, medical officer for Lupane district, said patients at the hospital were shocked by the boy's "bravery".
He said: "The patients who were admitted with him were wondering how he managed to do it.
"The good thing is that he wounded the outer layer of the foreskin.
So we had to keep him at the hospital to monitor him as he had used a clinically inappropriate tool so we were worried that it could have caused an infection."