The symptoms as well as the history of trauma due to fall (as mentioned in your post) suggest that the pain might be due to muscle pull.
There is nothing to worry.
It will subside on its own.
To provide symptomatic relief you can apply analgesic
ointment or take muscle relaxants.
Also make sure you do not put strain on your chest muscles.
If the symptoms persist or aggravate, then it will be better to consult your Doctor & get a proper physical examination done.
Wishing you a Good Health. Let me know if I need to clarify further.
Thanks & take care