Hi,
You should refrain from picking at the lesions as this could cause secondary bacterial infection.
This could be an allergic reaction to some unknown substance or secondary to insect bite etc or due to heat rash. This could also be due to dermatitis , eczema or folliculitis. But nothing can be said with surety without a clinical examination.
You should wash the area and keep it clean, apply calamine lotion at the site and take some oral antihistamine or antiallergic medications like loratadine or cetrizine for your symptoms. You could also use an over the counter antibacterial cream like mupirocin till you see your skin specialist.
It would be best to consult a skin specialist if the rash does not resolve in a few days. You should get the relevant investigations as advised by your doctor including blood work.
Let us know about what your skin specialist advises and if you have any other doubts.
Post us about how you are doing.
Regards.
could be shingles, they are painful too look likes chicken pox, go to a site about shingles and look at pictures to compare