Skin Cancer - Pimple turns into a black scab looking head

I think that’s a mole and not a pimple. It's important to know the difference between melanoma and a harmless mole. A normal mole is most often an evenly colored brown, tan, or black spot on the skin. It can be either flat or raised. It can be round or oval. Moles are usually less than 1/4 inch across, or about the width of a pencil eraser. Moles can be present at birth or they can appear later. Several moles can appear at the same time. Once a mole has developed, it will usually stay the same size, shape, and color for many years. Most people have moles, and almost all moles are harmless. But it is important to recognize changes in a mole -- such as its size, shape, or color -- that suggest a melanoma may be developing. Be sure to show your doctor the area that concerns you. If your doctor suspects you might have skin cancer, he or she will use one or more methods like skin biopsy to find out.