Thanks for your question on Healthcare Magic.
I can understand your concern.
By your history and description, possibility of
musculoskeletal pain is more likely because your pain is associated with movements of left arm and deep breathing.
So better to follow these steps for better symptomatic relief.
1. Avoid heavyweight lifting and strenuous exercise.
2. Avoid forward bending and sudden jerky movements of chest.
3. Avoid movements causing pain.
4. Apply warm water pad on affected areas of chest.
5. Take simple painkiller like
paracetamol or
ibuprofen.. Don't worry, you will be alright with all these.
Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks.