Well done for having a go at realism, I must say you did a good job at having a go.
You seemed to get the light right, if it is coming from the front, but perhaps try some more dynamic light and shadow, I know James Gurneys "Color and Light" is a fantastic book that will help you with that and it will make your piece much more striking.
Another thing to look at is study anatomy a lot more, the facial structure, getting the features to look right. This is crucial, and you have done a decent job at it, but to take it to another more professional level maybe study some anatomy books, like Loomis "Figure Drawing for All It's Worth" which would help an awful lot here, try drawing loads of different eyes, mouths noses, get a feel of all the different shapes and sizes that really makes a person who they are!
Just out of curiosity, if you used Photoshop, did you by any chance use the smudge tool? If so, then ban that tool and only use it when you really need to.
A better and more natural way to do this is to use (if you have a Wacom) the color picker tool with your brush set to pressure sense, then picking out the colors to naturally blend.
Also, colors in the face are not just one, if you look at your skin what colors do you see? Hints of browns, pinks and blues would be a good answer, try to incorporate that in your work.
The same technique applies to the shirt, and I notice you added the shirt after the skin, since part of the neck seems to have merged with the right shoulder.
Overall you did a pretty good job at realism, and all these techniques really apply in any style you do, so practice more and you will be awesome!