You can try wall angel stretches. Stand with your back against a wall. Bend your arms at a 90° angle and hold them against the wall. Slowly raise your arms above your head until you can't hold them against the wall anymore, then bring them back down. Repeat 10 times. If your back is only a little sore, try doing gentle yoga, which will also help stretch out the muscle. Restorative and yin yoga are specifically practiced to help stretch out and repair muscles. However, avoid doing yoga if you're experiencing severe pain.