In a blender, combine the frozen mango, 1 cup ice, mango nectar, tequila,lime juice, triple sec, orange juice, and salt and blend until smooth.
To serve, add 1 tablespoon chamoy to the bottom of a margarita glass, pour in the frozen margarita, then top with another tablespoon chamoy, a tablespoon or two of fresh diced mango, and a sprinkle of tajín.