Dull pain on back left rib travels to front under rib & occasionally lower left abdomen for 15 days. started after poor sleep posture & heavy purse.

Muscle stain: Sounds like a muscle stain. Try applying alternating cold and warm most compresses three times daily. Your choice of an over the counter antiinflammatory med like ibuprofen, aleve (naproxen) or Aspirin can help. Alternatively you can try a topical medication to apply directly to the painful area such as aspercreme or salonpas as directed. The symptoms should improve with time.