My lower left side of my back is very sensitive to touch (painful internally) and feels inflamed. it hurts when i move a certain way but not constant.

Probable muscle stra: This sounds like it's probable a muscle strain. It's very easy to strain muscles with or without strenuous exercise. The psoas muscle is the biggest muscle in your back and the back muscle that is most often strained. You can try ice for 20 minutes every 2 to 3 hours for the first 72 hours and then ice or heat whichever feels best. You can also try nonsteroidal's over-the-counter.