What is this lump in upper left stomach?

Ive had this lump the size of my thumb in my stomach on the upper left. about two inches below my ribcage. There is bruise over it so I umed it was a hematoma from hittng something and not noticing. Its been 2 weeks. Bruise is fading but lump is harder and more defined. certainly not ANY smaller. I have mild pain in that area when i twist or bend. If i just push on it it does not hurt. What could this be???!!