Small Semi Rounded Spot On Arm. Itching. Pain On Arm. Diagnosed Muscle Pain. Impetigo?

I believe I may have an Impetigo lesion on my right upper forearm at the shoulder. It started several months ago, and the only time I saw it was when I bathed. It was a small semi-rounded lesion of beige color and didn't bother me at all. Lately, I have had some pain in my right arm, saw my chiropractor and he said my problem is with my right front chest muscles. He told me to go home and not do what caused it. I use the computer often, and I thought I might be sitting too long at one time. I am a Retired Pediatric R.N. At first when the spot started itching, I thought it might be similar to a ringworm, but as I looked at these pictures on the internet, I believe it is Impetigo?