my left index finger will not bend down to 90 degrees (like a normal finger would) at the joint of the knuckle

this is not an injury it has been like this my whole life and it does not hurt. my right index finger bends down fine but my left finger will not go down. i can not make a fist with my left hand. my cousin says it can be extra cartalidge in the knuckles. should i consult a doctor for it or what should i do?