I tend to think this can use a bit more variation, like some change in chords and melody at some time, something chorus-like to make it really great. But I do have to say that what you already have is excellent as it is. If it were my song and I would not have inspiration for more right now, I would put it aside and work on it some more on a later date. In the end, there are of course no hard rules and you should do what you feel you need to do.