Why am I getting aching pain in my legs and bum 1 year after my BBL?

Hello Doctors, thank you for taking time to answer. I had a BBL September 2017, and I am over one year post op. I used to get pain when sitting for over 30 minutes, but now it is constant. It's a residual pain, like the pain you get after you knock yourself. The pain is specifically in my hips & the side of my thighs. Please offer any advice you have, I would be extremely grateful? Many thanks.