What Causes Dry Sores On Arms And Shoulders?

I have sores on my arms and shoulders I pick at them because they are dry and pull the skin. The middle part looks white I have had them for about 2 months. A couple of them started when I hit my arm on something and it broke the skin. I keep them clean and wear long sleeve shirts because I don't want anyone to see them. They are leaving big scars on my arms. What can I do to get them to heal quicker?