Usually when it's a fall on the buttock..the tail bone coccyx can get injured..if it's a mild fall it can be just a soft tissue injury which takes about 4 to 5 days to heal..if it's a bony injury it can take upto 4 weeks to heal..if pain is severe better to see an orthoapedic consultant and get an x-ray done..

• Contrast bath---It is a form of treatment where a limb or the entire body is immersed in warm water followed by the immediate immersion of the limb or body in ice water. This procedure is repeated several times, alternating hot and cold. Note that the treatment should always end in the ice water, as heat will induce the body's inflammatory response, while cold helps to decrease inflammation.

If you hurt your back - better to get it checked soon. If it is tail bone - most treatment is pain killers and rest. If you are in doubt - consult orthopaedic doctor.