Should I cut off my finger?
That wouldn't be good. Why do you want to cut off your finger?
I don't want to complete my exams
Not wanting to take your exams is normal but hurting yourself to get out off them is not good. You could cause serious harm to yourself that will affect you for the rest of your life.
I don't care. I'm already thinking of taking a knife and cutting it off.
Stop, it is not good to hurt yourself permanently in order to get out of a test. Even skipping the test and failing would not ruin your life as much as cutting off your finger would.