Yes, the GP is the doctor to see first. The GP will know if the skin lesion looks concerning and if necessary will recommend a specialist or biopsy. I have some gross looking lesions on my back and leg and my GP always reassures me--"those may look bad but they're harmless" and has never done a biopsy. Some lesions they can tell at a glance are benign. But a lesion that overnight goes through a big change is something to pay attention to! I'm glad you are seeing your doctor right away.