Lump on lower left ribcage when sitting

Hi,

I recently had an accident which involved me falling of my bike. I landed on the pavement - I'm even not sure whether the ribcage took a hit, though - I just thought I'd mention it. Anyway, a few days later I developed lower ribcage pains that were most severe when lying down - I assumed they were related to my accident. By and large the pain has subsided - it is now a minor nuisance, barely noticeable. However I developed a lump in/on the lower left ribcage that is most noticeable when sitting or lying down. It's not visible from the outside.

What could have caused this? I was thinking cracked rib, or maybe some spleen trouble?

Thanks