Seems like you have developed a pyodermic lesion...It is a bacterial infection of the skin...
So firstly,,keep the area clean..do not apply any oils,moisturizing creams over the affected area..clean the lesion with an antiseptic liquid twice a day and use a topical antibiotic
cream like mupirocin
over the lesion....If inspite of the above measures, there is no relief, then you might need a course of oral antibiotics
,,,In that case, you will need to visit a dermatologist
Hope it helps
Dr Geetika Paul