Brief Answer:
As explained below.

Detailed Answer:
Hello and welcome to Ask A Doctor,

Thanks for your query.

I have gone through your query. What is your age? Did you hurt or injure yourself recently?
It looks like a muscle pull or strain.
I would suggest you to take these medicines:
Tab. Etoricoxib 90 mg 1-0-0 for 5 days after food
Tab. Nusaid P 0-0-1 for 5 days after food.
Hot fomentation to the affected area.
Omni gel or Volini gel for local application.

If it still doesn't get better it is best to meet a physician or orthopedician.

I hope this helps you. Please feel free to discuss further.
Regards,

---