What Causes Painful Bruises On Left Side Of Abdomen?

I have two bruises on the left side of my abdomen they are both painful to touch, but i sustained no injury to this area so I am worried the first bruise is brown and the normal color for a older bruise on me the second is a purple/blue and is incredibly painful to touch any idea what this could be or what my next step should be I would appreciate it thank you in advance.