Chiropractic adjustment will help. Apply Hot Fomentation twice daily. Avoid bending in front. Postural Correction- Sit Tall, Walk Tall. Extension Exercises x 15 times x twice daily - lying on tummy, take left arm up for 3 seconds, then bring it down, right arm up for 3 seconds, bring down. Bring right leg up, hold for 3 seconds, bring it down. Then right leg up and hold for 3 seconds and bring it down. Repeat twice a day- 10 times Bhujang Asana -- Lie flat on your stomach, keeping the palms out, bend the neck backward, take a deep breath and while holding it for 6 seconds, raise the chest up. Release breath and relax your body. Repeat the exercise 15 times twice daily. Core Strengthening Exercises- Straight Leg Raised With Toes Turned Outward, repeat 10 times, twice a day. Chiropractic treatment.

Visit a physiotherapist for optimal pain relief

You are having back due to muscular imbalance. 1- Some of the muscles are overuse. 2- Some are weak 3- Some are tight. After long standing and walking Pain comes due to reduce stamina of muscles. So you need to visit or consult with Physiotherapist for Rehabilitation and strengthen your back muscles, release tight muscles, and for mobility exercise.

Continuous long standing is your problems. Back muscle are weak So tk physiotherapy session and after this start  strength exercise of spine .

Postural stress is common when r standing for long duration.thag may lead to tightness n spasm in back

Consult a physiotherapist.

Please consult a therapist for exercises. I think this is mainly because of stiffness in ur back and muscle weakness. Therapist will evaluate you ,give some exercises,also she will give some ergonomic advice as to what can be done to improve ur posture and precautions to be taken to reduce the back load. I think this will improve with 10-15 days of regular back exercises.

You belly may be enlarged or stiffness in back muscle cause this problem .forward bending for 5 times will help you relieving the pain.