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Moles can be of various category as Dysplastic naevus,halo naevi and blus naevus and most of the changes that occur in mole in shape,size are benign but any mole that is unusual should be examined.Since it is associated with pain and has blurred edges it definitely requires a clinical examination as evaluation is the most important step for coming to diagnosis.
Kindly consider visiting a Physician earliest for examination and if required he might advise Biopsy.Meanwhile avoid unnecessary exposure to sun.Keep covered in sun and apply sunscreen.
Take Care!