Based upon your answers, your back pain could be due to a strain or sprain related to one of your daily activities that stressed the joint, tendons and/or ligaments around the back; it should improve over time.
To decrease pain, avoid overuse and try a heating pad (especially if pain has only been present for a day or two). Over-the-counter pain medications, topical treatments (such as Icy Hot or Ben Gay), or the application of ice might be helpful.
If symptoms are getting worse or do not go away, consult your physician.
More information about your back pain may be helpful to better understand why it is hurting.