Back pain is often due to bad posture. To improve your posture, you should do these poses:
Cobra Pose (Bhujangasana)
This pose is perfect to relieve any upper body stiffness, from your upper back to your shoulders. Get into this pose to increase flexibility in your lower back and to strengthen your shoulders and upper back.
Warrior II Pose (Virabhadrasana II)
This pose is a great one to create balance and a nice posture. Relax your shoulders. Lower and open your hips.
Child's pose (Balasana)
This pose is super calming for your mind and elongates your lower back. Folding over your legs releases the pain you get from sitting in a chair all day. Stretch your arms far forward to increase the length of your torso.
Downward-facing dog (Adho Mukha Svanasana)
This pose strenghtens your shoulders, arms, upper back, hamstrings, calves, ... Such a great stretch to relieve your back pain! Press your shoulders to the floor and your heels towards the mat.
Standing forward bend (Uttanasana)
I love this pose to reduce my back pain. If your hamstrings are being to resistant, bend your knees slightly.
Enjoy these moves and reduce your back pain!