1. Examine your technique
By far the biggest cause of back pain in bowlers is a mixed action. That is when your hips and shoulders are not in line when you enter your delivery stride.
The reason this is bad for the back is that your lumbar spine is not designed to twist. It can twist a little but repeatedly asking it to do so (such as when you bowl a spell) will eventually cause an ache that perhaps grows to a full stress fracture
2. Stretch your hips
Very often with back pain, the symptom is not the cause.
I see players, even at professional level, stretch their lower back when warming up. As we already know, the back is not designed to stretch. It's the equivalent of picking at a scab: Feels good but not the right thing to do.
Instead, take a look at your hips. Modern lifestyles of inactivity and sitting in daily life lead to inflexible hips with your lower back taking up the strain of reduced range of motion. So the answer is simple: Stretch your hips, not your back. Stronglifts has an excellent guide on hip mobility here. You can do this stretching every day without fear and should at the very least be doing it before any physical activity (cricket included).
3. Strengthen your core
The muscles in your back and stomach area that can't be seen (even if you have a six pack) act as stabilisers for your back. They hold the spine in a healthy position and work on a subconscious level. That means you can't strengthen them with crunches.
Instead, focus on the body awareness that will help your body hold the spin in place. Yoga can teach you the basics of body awareness as can a corrective exercise plan designed by a qualified sports medicine practitioner.
Combine this with core stabilising exercises like planks and side bridges and you begin to bulletproof your back.
As Gray Cook says, the focus is not on creating more power from the core, but learning how it can stabilise your back while movement is occurring.
4. Warm your muscles
It's common in England when the season starts in April to be less than warm. It's also common to see club players, on the first day of the season, getting out of their cars after months of inactivity and going out to bowl or bat.
I'm sure it's similar all over the world. No wonder the back starts to complain.
It's essential to warm up before play in any conditions, especially the cold of the English spring. Build up to the big stuff by warming up for a few minutes.
The same applies to any heavy or long lasting activity. A few minutes of dynamic stretching will make all the difference.
5. Stand up
As we know from our hips, modern living is hard on the body. We sit down to drive, sit down and hunch over the computer and even sit down on the machines in the gym!
If you spend a lot of time sitting, just standing up will do your back the world of good. Once an hour or so, get up and do something: get a drink, walk around, do a couple of static stretches then get back to sitting. It should only take 1 minute.
The same also applies if you are on your feet all day. Take a few minutes every couple of hours to sit or lie down. Your back needs the variety.
6. Get a massage
Everyone gets knots in their muscles through daily use, even if they don't play cricket. Massaging the soft tissue can work them out, restore full function to your muscles and reduce pain.
You can get a professional to do it, or even do it yourself with a foam roller.
7. Move your butt!
Physical trainer Keith Scott deals with a lot of clients with back pain. He claims 99% of his clients have weak glute muscles. Sitting all day shuts them off and cause the hamstrings to take up the slack which puts pressure on the back again.
The simple solution to this is to reactivate the glute muscles in two ways. First, as part of your warm up include movements like glute bridges. Second, in the gym train your glutes directly with exercises like single and double leg deadlifts.