The answer is yes. Sitting on something like this can cause lower back pain.
This can cause you to become lopsided with a rounded, banana-shaped spine. This hunch-like position puts more stress on the back and spine and can even cause a slouchy posture with slumped shoulders. Muscles work harder to compensate, and joints become stiff and achy.
The sciatic nerve gets pinched between your wallet, your gluteal muscles, and your hip. Even after a short time, the sciatic nerve can become irritated, causing discomfort that ‘zings’ down the back of the leg and into the heel. This condition is so commonplace that it has earned the nickname, “wallet neuritis,” describing the inflammatory response that happens to the sciatic nerve due to sustained compression.
What to do?
Your best bet is to remove it from your back pocket
entirely before you sit down or get in your car. You could switch your
wallet to your front pocket – but be warned that prolonged use of a wallet in this position can also pinch a nerve between the thigh and torso, especially when you’re in a car. This can create discomfort as well. While at work, place the wallet in your desk, locker, or somewhere safe. You should also avoid anything bulky and stick to slim wallets or money clips that hold only the essentials.