The good part is that many methods can resolve this issue and In just few minutes of your time.
Lie on the ground on the back and stretch the leg hamstring. Pull it upward and after half a minute switch the legs.
Feet are on the ground together, sit and hold the ankles. After half minute, make a break of 10 sec and repeat.
KNEES TO CHEST
Lie down and pull one of the knees to the chest, after 30 sec switch legs.
Lie down on the back and cross one leg with the other. The back must be straight for half minute and then repeat and switch legs.
Again lie down on the floor and one leg must be over for 90 angle. Cross it over the raised other leg. After half minute switch the legs and imitate sitting on a chair down on the ground.
On the floor, lying, one leg is backwardly pulled. After 30 sec, switch legs.
One leg is forward and the other back. Bend and the back leg must be straight, after half minute switch legs.
WHAT MAKES THE BACK PAIN?
Many factors can impact this issue. You are sedentary, or too much standing in one position, but with such workouts and stretches this problem will be gone.