What Could Purple Spot On Arm That Flakes And Is Dented Indicate?

Hello. I am a 21 year old female, currently vacationing abroad. For the past month I've had a splotchy purple mark on my upper right arm. It is a little bigger than the size of a quarter. It is not itchy but when I scratch it with my fingernail, it gets flaky. Also, it seems that this area on my arm is slightly dented inwards. It is not painful so I am waiting to go back to my home country to see my for PCP but am starting to get a little worried. Thank you for your suggestions.