Back pain can occur due to bad posture, pressure on the back muscles and from taking too much weight at once. try out the following for controlling the pain.

When you get a sudden back pain, lie on the bed and take rest for at least 2 full days,
Apply an icepack on the effected area. After half an hour keep a hot pack. Repeat if needed.
Keep pillows under the chest and legs and lie on your stomach. Dip a towel in boiling water, twist the water out from the towel and apply it to the affected area. Steaming the area also will reduce the pain.
Heat some coconut oil or mustard oil mixed with a little camphor (Karpuram) powder and apply on the effected area.
Heat some coconut oil mixed with crushed dried ginger and garlic. Apply this warm oil to the affected area and place a hot bag over the area.

But, if you get back pain without any particular reason or if it is accompanied with chest pain, breathlessness, stomach pain, fever etc or if the pain does not go or lessen even after 2-3 days or if the pain spreads to other areas like legs, knees, feet etc. show a doctor immediately.