Lower back pain is common after workouts, After all, your back plays a big role in a number of exercises. Part of building muscle involves creating slight tears as you burpee, plank, lift, etc. However, the microtrauma associated with this can sometimes result in pain. This type of pain could last for up to 72 hours after you work out.
Specific muscles in your back become overstimulated and under-stretched, esp if your sitting at a desk all day, driving in a car, watching tv with little back support.
The right stretches help calm low-back spasms,
Lie on your stomach and place your hands on the floor as if you were starting a push-up. press just your upper body up, allowing your lower back to relax by keeping your hips close to the ground. Hold for a few seconds. Also our cat cow Britney is a great exercise or, Lie on your back, tucking the kneed into your chest, when hugging your knees rock forward and back.
Applying ice/cold pack to your back first, Once the inflammation has subsided, use heat therapy, I would use a warm hot water bottle. When you apply heat, it improves the flexibility of soft tissues, movement of muscles, and overall functioning of the back.
When in doubt always rest, up to 72 hours, but try and get in some brisk walking. If the pain lasts longer then visit your local gp / physio