The boy said to me,' Go away, be jealous'.

Well, you have to look at the specific situation.

For example, I, um, if I were a good friend, I might say this just for fun.

But if I like this person, maybe this joke will bring real jealousy in it (although I just like it, I am not qualified for jealousy at all)

Well, your own judgment is the most correct. After all, no one else knows your relationship and familiarity.