If you look around the web you will see a lot of tutorials on how to retouch a photo. A lot of the time they are a professionally done photograph that is destined for a magazine or print ad. The problem with those is a large percentage of the people looking at retouching may not have a professional camera. A lot of people have point and shoots or phones.
Yesterday I was fiddling around in photoshop and I came across a picture of myself I took recently with my cellphone. It was an injury I sustained while helping my dad put up treestands in preparation for deer hunting. I sliced my finger open with a limb saw. It was a pretty bad injury but since I don't have health insurance I went for the next best thing. Superglue. Yep, I superglued my finger shut (among other first aid things like proper cleaning, wrapping, etc). As of writing this the wound is healing nicely and I am going to have a kick ass scar. To go back to the photoshop thing, I was fiddling around and I played with the spot healing brush and clone stamp tools. I fixed my finger without health insurance!
This goes to show that it does not matter what camera your photo was taken with. You also don't need to only touch up professional photos. Play around with what you have available. Learn what does and does not work. It is a hell of a lot better than downloading specific tutorial material that is guaranteed to work because you won't run into the pitfalls a real photo can give.