Hi!
The easiest way would be to make an appointment with derm and find it out. Because,at one hand, it really could be the dead skin that sometimes comes off, especially in summer, after sunbathing. But at the other hand, it might be something more serious, and it your family has a history of melanoma cases, it`s better for you to check it and forget it.
Moreover, I can suggest you reading about virotherapy, which is not only a cancer treatment, but it is also often practiced as immune system activitator, thus decreasing the possibility of the person getting a melanoma ( I mean those, who are at the high risk group of getting melanoma). So maybe you could benefit from something that prevents such severe cancer.
Hoping, that your worries are just worries,
Beatriice