Indentation after my 2nd C Section. What is causing this and can it be fixed? (photos)

I've had my 2nd C section 3 1/2 mos ago and it left a big indentation in my lower left belly, just above the c section incision. My OB doesn't know why it happened and she's never had this issue before so she told me to inquire with a PS. She's guessing that it's old scar tissue from my previous c section back in 2013. I'm 45, 5'1" @ 145 lbs currently so I would like to lose at least 15-20 lbs more before I think about TT. Would I need a full TT with muscle repair? Could a TT fix my issue?