It is likely you have pulled a muscle while playing. Take painkillers, keep mobile, do gentle stretching and also apply heat packs with a hot water bottle. The pain will gradually get better. Next time before starting to play do warm up and stretching, it will help.

Core Strengthening Exercises. Back Stretching. Do the cat/cow stretch. Postural Correction- Sit Tall, Walk Tall.

Hello there...... You may be able to avoid back pain or prevent its recurrence by improving your physical condition and learning and practicing proper body mechanics.... Exercise. Regular low-impact aerobic activities — those that don't strain or jolt your back — increase strength and endurance in your back and allow your muscles to function better. Build muscle strength and flexibility. Maintain a healthy weight. Being overweight strains back muscles. If you're overweight, trimming down can prevent back pain.....