is this normal?

I had a baby 4 months ago by c section and have got a lump just above my naval its from my breast to my belly button its not painful but it does stand out i noticed it straight after i had my baby but thought it was normal after having a baby i have been told by afew friends that this isnt the case and i am getting worried now, i went for my 8 week check up but doctor only looked at my ankles and my breast (breast feeding) he never looked or felt my stomach i am only 21 and havent been sent for a smear either is this any thing to worry about and if it is what could it be?