Most professional graphic designers use Photoshop to edit and touch up images; however, many inexpensive mobile device apps and even free suites will adjust your cropping, exposure, sharpness, contrast, and color.
Taking a closer look at the image on a screen may reveal scratches or dust that went unnoticed during the photography session. Take time to remove these if your application has photo editing and/or repairing tools. Photoshop offers several options such as the Clone Stamp and Patch tools. There are plenty of online tutorials to help new users with editing tricks.
-Brad Wass, Gyford StandOff Systems