Oh, I thought a muscle injection... did you have X rays or MRI is there a spinal or cervical vertebra problem that showed on imaging?
I would ask Dr more questions , like why he is thinking epidural etc? (spinal stenosis, spinal disc herniation?)

Epidural Injection - Google Search

TOS can be brought on by a whiplash event, many general MDs are not up on all the info , so visit our TOS forum and explore the sticky threads so you can advocate if needed for best care..