I get pains in my lower chest on the left side when i wake up or haven't moved for prolonged periods of time. hurts to take deep breaths or stretch.

Tough to say for: Sure with this brief description. It sounds like pain with muscular origin, but it could be pain from internal organs such as lung, diaphragm, spleen, or stomach. It could even be shingles. The most serious problem is blood clot or infection in your lung, so have it checked out.

Check with your doc: No easy answer. Check with your doc to avoid complications.

Costochondritis: Chest wall pain that occurs with movement or deep breathing in someone young & otherwise healthy are often due to inflamation of the ribs or strained muscles adjacent to the ribs. This is often improved over time with rest and possibly anti inflammatory medications prescribed to be taken by mouth or topically as a cream/gel rubbed on the affected area. Still it needs eval by a dr t.