“Pain after silicone injections on butt”

Seeking help:

I had a silikon or PMM, injection (the doctor tlod me that he inject metacril, but i know this is not true) into the buttocks 2 yrs. ago. I had no problem, but now i have this slight pain in the right buttock only when i sit for log hours working on the office. It’s not too painful att all, but, I only feel it like when I try to touch my toes. I did an MRI and nothing came back. the result said that i have liquid in my buttock ,so what you think I should do? Another test, maybe? There is no lump, redness nor marks. Might it be an infection or went in muscle? thanks.