I've been having this uncomfortable pain just below my left breast, and it's only on one side. I've started working out recently. Could this just be muscle pain from exercising, or should I be worried about something else?

The pain you are experiencing below your left breast could be musculoskeletal in nature due to your workout routine. However, it is important to rule out any other potential causes such as costochondritis or even cardiac issues. To help alleviate the pain, you can take over-the-counter pain relievers like ibuprofen (Advil) 400mg every 4-6 hours as needed for muscle pain. Additionally, applying a warm compress to the area and avoiding strenuous exercise that exacerbates the pain may also be helpful. If the pain persists or worsens, it is advisable to consult with a healthcare professional for further evaluation and management.