Thanks for writing to us.
The firm lump in the muscle that you can feel is likely to be due to a fibroma
or a myoma. It can be an area of fibrosis
after an hematoma
or an injury
. An MRI scan will help in the proper diagnosis. It is not likely to resolve spontaneously without a treatment.
I hope this information has been both informative and helpful for you.
Dr. Praveen Tayal