What could cause a back ache to show up four days after initial trauma?

Need more details: Many times, the minor symptoms after trauma appear a few days after the accident. But it really depends on what happened. In minor trauma, t may be muscular aches and pains which tend to show up a day or two later. If the accident was more severe, like a car crash, back pain can be a sign of internal injuries. In this case, you should see your doctor soon to have it checked.