Hello Ho welcome to dermatalk forum. Doesn't look like melanoma to me. But anyway few questions... How was the lesion when u first scratched? was it inflamed with pus inside it? was it tender (painful) on touch? Was it hard, raised, soft, flattened?
Although the picture is not clear (a good clear closeup pics would be helpful) I don't think its that scary, it could just be Furuncle (boil).