As the size is increasing and redness
is increasing we have to rule out infection, hence a consultation is a must.
Other indications for infection ( and consequently antibiotics are ) , frank pus, pain on touching ( tenderness) and fever
The area where the problem is there is not exposed to air, and sweating can occur. This can aggravate the problem.
Other possibility is some insect bite allergy
. The insect need not visible. In the cloth it might have stuck when the cloth was hung for drying.
Itching indicates allergy best first aid
is apply tap water in a cloth over the area.
If in India, once gut worms have to be thought of
the chemical we use for washing and bathing also should be thought of