It seems to be a bug bite
or an insect bite. You should take Tablet Benadryl
1 tablet twice daily for atleast a week. This will make you sleepy. So if you cant afford that, take Tablet Allegra
180 mg 1 tablet in the daytime and benadryl tablet in the night time.
Also, apply calamine
lotion and keep the area clean. This should take about 1-2 weeks to resolve completely