Thanks for the query.
You might have developed a sebaceous cyst
It is a cyst appearing mainly on face and back.
The main feature is expression of white cheesy material.
Surgical removal is the only available treatment.
Please meet a dermatologist
and discuss regarding this.
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.