I Had A Quad Bypass. Now Right Below My Sternum,

I had a quad bypass. Now Right below my sternum, when I try to do stomach crunches, I get this large bump that runs from my sternum towards my belly button. Like size of half a hotdog on a bun. Never had it before surgery ( I was in pretty good shape prior to going in for my surgery, did lots of crunches )
Had my check up today and Dr says that is NOT common, but didn't know what it was.
is it just muscle that needs to be retightened???