My brother attacks me and chokes me. would i be at fault if he got seriously injured?

my brother attacked me and i got to a knife. i tried to defend my self but i couldnt bring myself to cut him. i cant cut my own sibling no matter what he does. also if i stabbed him would i go to court and be in huge trouble. hes kind of crazy and i dont want to call the cops . by the way im 14 and hes 17. i dont lke attacking other people or punching them in the face or head but if i have to i would. if it meant not getting anymore black eyes