Welcome to Gaia! ::

Overall looks good. The eyes, nose, and the mouth are done correctly. I think you put too much emphasis on the tip of the nose, I would reduce that a bit. I'm not too sure about the hair, I think you could've done a better job shading it instead of trying to draw each "segment" of hair. Because of the way you did the hair, it looks almost plastic(also it's preferential). Also, if you shaded the neck, the head wouldn't look like it's floating in space. I think it's a very good portrait overall. =)