Lips are not oriented with the face.The nose hole is a touch too big and your brush used for shading seems a little too hard.
Very nice first attempt though considering you used just a mouse.
And yea in the very unlikely case that you don't know, always draw on paper first to know how to go about.
Keep painting !!
Don't take this as negative criticism pal, just letting you know how i think you can make this better.
EDIT : Considering the person has no face hair it has to be a female celebrity, though a female should have a little softer features.