Almost all the above comments made about low back pain apply to the thoracic spine region which extends from where your neck merges into the shoulder area down to just above the lower back. If the onset of pain is due to a straining event and there are no leg symptoms, there is no hurry to see a doctor unless it persists for over a month and does not respond to heat, over the counter anti-inflammatories and activity limitations.
Thoracic back pain that begins without an injury probably is due to some disc degeneration or joint inflammation and usually clears up in a week or two. If it persists beyond a month, see your doctor.
The thoracic spine is pretty resistant to fracturing with a fall, so unless the fall was from a considerable height, immediate treatment for such mid-back pain is not usually necessary.