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Unless the GP positively identified the type of skin change, without wanting to increase any anxiety, I think you should insist to be referred to your local NHS dermatology clinic. They are best placed to have a closer look, which is probably what’s needed.
Could be dermatofibroma, As my 15 year old son has a few small dermatofibroma on his leg.
If you are concerned I would push to be referred to the dermatology department, they would able to tell you.