Hi,
These white little bumps could be miliaria or heat rash. These looks like a red cluster of pimples or small blisters caused by excessive sweating during hot, humid weather. It is more likely to occur on the neck and upper chest, in the groin, under the breasts, and in elbow creases. The best treatment for heat rash is to provide a cooler, less humid environment. Continue using your sunscreen. Drinking plenty of fluids and keeping the affected area clean and dry may also help. If it persists, it would be best to see your doctor for further evaluation and management. Take care and keep us posted.
Hi
This may be a case of tinea versicolor, a form of yeast infection which may present with a lightly colored pigmentation on the skin. This however may present with a light scale and itchiness may be present. Another differential is keratosis pilaris which may present as white pigmentations on the skin especially behind the arms .They may have a sand paper feel on them when you run your hand on the affected surface.
This does not sound serious. Just continue to observe this. It is necessary to rule out vitiligo here which is a stark white well demarcated patch of skin usually appearing symmetrically. At this point, I do not think this is your case.