I agree overall with the advice here. I tell every incoming intern that it is almost guaranteed that they will get one evaluation that they think is unfair, unreasonable, one sided, or just plain wrong. There's no grades anymore, so the important part is to realize that even if you think the evaluation is unfair, it does reflect what that evaluator thought of your performance. Maybe they didn't see your best? There is usually something to learn from the evaluation, filter out the noise and find something to improve.
If you think the evaluation is actually wrong -- i.e. they have evaluated the wrong person -- that's a different story.
You mention "confusing something that happened between the medical student and me". This is somewhat unclear. It could be intepreted that something the student did is being incorrectly assigned to your performance, or it could mean that they saw "something between you and the student" (i.e. an interaction) and have misunderstood what that was due to lack of context. If the student did something bad, and you were the resident who was supposed to be supervising this student, then it's not completely unreasonable that the problem is assigned to you (although in that case, I would have pointed out your failure to adequately supervise the student rather than "the problem" itself).
Your options are to do nothing, and this will get reviewed with you at your 6 month eval (which most programs do). Or, you could explore it further -- but you need to do so carefully and tactfully. You could send a note to a mentor / PD / Chief (depends on the field you're in) saying "I received this concerning evaluation which is out of character of the rest I have received, and I want to make sure I address it and improve. From reviewing the evaluation, the main points where I need improvement appear to be (insert stuff here). I also noticed that Dr. X commented upon (insert "the confusion"), and I would like more feedback regarding this as my recollection is somewhat different. Regardless, my goal is to improve my performance, I understand that I have not met Dr. X's expectations, and I want to improve and move forward".
Something like that. Non confrontational. Own the problem. Ask for more information. if there's a confusion, it will be discovered.