In 2012 had glass shards removed from buttcheek after a freak accident. Now there is a hollow and it's uncomfortable. Options?

I had to have glass shards removed from my cheek. A plastic surgeon did an amazing job, minor scarring, the contour is intact well, given the situation. She explained that because she had to remove layers of, I guess tissue and stuff, there is a "hollow" that is not filled in with fat/muscle/tissue whatever was there before. Over time it's gotten more uncomfortable to sit and I wish I could just fill the hole. Is that a solution? If so, how do I mention it? Is this common after surgery?