Hello,
It could be a freckle, mole or solar lentigene.
Sun spots or lentigines, are harmless, flat, brown discolorations of the
skin which usually occur on the back of the hands, neck and face of people and are caused by the skin being exposed to the sun. The only way to prevent age spots is to use liberal amounts of sunscreen before the age of forty, avoid the sun, and wear protective clothing. The newest treatment for age spots is an alpha hydroxy acid gel or beta hydroxy acid gel.