Just took a couple of seconds with the image you provided but it was pretty easy. It would be best with a rendered layer but if you didn't have a detailed background it is pretty simple to do.

Open your image, go to filter/liquify and hit the kinks, just follow the direction of the hair strands before the kink and smothe it out. You can sort of just hit the kink itself and form a little bit of a natural curve or you can go up from the kink and then try to smooth it to the new angle.