welcome to HCM,
as per the description you have been given , its really hard for any physiscian to say the correct diagnosis. dermatological conditions should be seen with a eye and examined properly to come to diagnosis ..but any way i will list out the causes :
1. MAY BE A TINEA
2. MAY BE T.VERSICOLOR
3. INSECT OR MOSQUITO BITE
HOW EVER , MY ADVISE IS TO CONSULT A DERMATOLOGIST
AND , GET EXAMINED PROPERLY, HE WILL TAKE CARE IT..