Student or Learner
<My sweet and respected teachers> 'I'll mutilate your fingers' means 'I'll cut your fingers' right? 'Please do not mutilate this forum by changing its features' right 'Do not mutilate my book by drawing lines' right?
'mutilate' means to inflict a violent and disfiguring injury on a person or animal, which may involve the severing and removal of a body part. It can be used more figuratively as in the mutilation of a film by the removal of scenes not passed by the censors etc.
Your examples lack the sense of inflicted violence; and it would be a hand that was mutilated by the violent loss of a finger, as opposed to just a 'mutilated finger'.