What Does A Lump Around Waist After An Injury Indicate?

I was in an accident a couple weeks ago & was left with no injuries other than minor bruising around my waist from the seatbelt. I have felt a lump under the skin of where the belt bruised me but left it untreated & skin returned to normal color. I have been working out with high intensity & it does not hurt so I don t believe its a hernia, but I still feel the lump in there. What is your opinion?