Thanks for your question on Healthcare Magic.
I can understand your concern.
By your history and description, possibility of pulled muscle is more likely.
So follow these steps for better symptomatic relief.
1. Avoid movements causing pain. Avoid sudden jerky movements of chest.
2. Avoid heavyweight lifting and strenuous exercise.
3. Apply warm water pad and ice packs alternatively.
4. Take simple painkiller and
muscle relaxant drugs.
You will mostly improve with all these in 1 week.
Of not improving then get done
ultrasound of local part and
x ray chest to rule out internal pathology.
Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks.