Your symptoms are more alike to a pulled muscle than other problems you suspect.
I'd suggest to :
- apply warm clothing to the pain area (but first check for any bruising or injury
- apply local analgesic
- take acetaminophen/ibuprofen
for the pain
If no improvement within a week, can consult your physician for further evaluation.
At last, avoid quick movements such as stretching or heavy coughing.
All the best!