Mild stabbing/gnawing pain on left lower rib for months. lasts a few seconds-minutes every few hours. same area swollen after eating. i'm 20 years old?

What I'm thrown off: by is your description of the location.."left lower rib." Otherwise this suggests GI dysfunction, i.e. dyspepsia/reflux, but almost always the location would be mid-lower chest/upper abdomen. A pain over the ribs suggests connective tissues: cartilage/tendons/etc. I might eat plain diet/try daily anti-acids/Pepcid/or Nexium for a week. Not better--see Doc for evaluation. Stay well:)