Cuts in dreams are all about feelings of emotional injury in your waking life. Here's a link to the full definition:
dreamdoctor.com/dream-dictionary/definitions/cut.html
Based on that and the setting of your dream (school), the guy in your dream (the one you like) and what he does... your dream would seem to be about your feelings of emotional injury caused by this guy in your waking life at the time of the dream. Don't get distracted by the design of the cut or where and how he cuts you... the fact is, you're feeling hurt by him. Blood is another symbol of emotional pain:
dreamdoctor.com/dream-dictionary/definitions/blood.html
Your dream is alerting you that you are experiencing some hurt at the hands of this guy, so it's time to protect yourself and your heart. Find someone who will bring you joy, not only in your waking life, but in your dreams.
Good luck!