It would be wrong. The idea is to let the listener know that you're asking a question. If there is a question word like Nereye, it's enough. It can be any question word like who, which, when, how etc. If there is no question word in your sentence and it's nonetheless a question, it's a yes/no question. In that case you add the extra mı/mi/mu/mü-particle somewhere in the sentence (with the personal suffixes attached to the particle should you choose to use it immediately after the verb), so that the listener knows that what he just heard was a question, rather than having to judge merely by your intonation whether it was a statement or he's expexted to give an answer.
So the previous sentence was 'eve mi gidiyorsun' which was also 'are you going home'. Please could someone explain the difference in nuance between the two? Is it that the asker in this sentence is surprised that the person is going anywhere, but the asker in the 'eve mi gidiyorsun' sentence is asking if they are going home instead of to the park (for example)?