Is It Possible to Remove Injectable Butt Augmentation Substance?

Silicone injections and silicone nodules in the buttocks can be treated effectively using conservative measures in the primary stage of treatment and surgical measures in the secondary and plateau phases of silicone treatment. I characterize these three phases as such:
Karamanoukian protocol for silicone injection treatment:
Primary Phase - Conservative: Reduction of Inflammatory and Infectious Component of Silicone Injections
Secondary Phase- Maintenance of Inflammatory Component of Silicone Injections
Plateau Phase - Surgical Measures to Reduce Deformity
I routinely treat patients from Asia and South America with a similar problem. In your particular case, I would address the inflammatory component of your injections for at least six months and then transition to a corrective modality to remove th silicone nodularity.

There is no real way to provide you specific advice without first figuring out what material was injected. It would be best for you to meet with a board certified plastic surgeon who can give you the advice and treatment you need. 

I recommend that you consult with an experienced, board certifies plastic surgeon.  I have taken care of many patients who have had similar buttock irregularities following the injection of illegal fillers.  The corrective options really depend on how soft the buttock tissues are now and how amenable the tissues are to contouring by liposuction, fat grafting, or buttock lifting techniques.