Thanks for posting your query at DoctorSpring.com. I can understand your concern.
From the picture, it looks like a furuncle. A furuncle is a bacterial infection of the skin.
However, it would be better to visit a doctor who can physically examine it, as it's difficult to judge it's dimensions and origin from the picture.
The treatment for it would be a course of oral antibiotics like erythromycin. Application of fucidin cream or neosporin cream would be helpful.
You would need a prescription for the oral antibiotics and the fucidin cream.
Hope this helps, Please let me know if you have any queries.