Hi. Im 16 Years Old, Just Got Back From A

Hi. Im 16 years old, just got back from a trip to mexico. I developed a triangular brown spot on my dominant hand while there and then today (2 weeks after returning) 2 more brown spots appeared on my non dominant hand. They don't hurt or itch. The larger one that appeared 1st is sliiiightly raised. DO you know what it could be??