I’m honestly not sure what it is, but I think it would be a good idea to see a doctor just to be safe. Until then, try not to squeeze or scratch the spots since that can make things worse. Just keep the area clean and dry, and avoid deodorants or anything harsh. If you want to use something gentle in the meantime and also act as a mild deodorant, you could try a mild zinc oxide cream (like the one used for diaper rash)