Welcome to the forum.
From your history it seems that you might have Infected Sebaceous Cyst
As you are having scoliosis
chances of having Cold abscess
should be ruled out.
Consult orthopedic surgeon and get examined.
I hope this is helpful to you.
You can consult me again directly through my profile http://www.healthcaremagic.com/doctors/dr-saurabh-gupta/64132
Dr Saurabh Gupta.