Kidney stones can certainly present with pain, and this can be located in the region of the lower back / flank area. Depending on where the stone is, it may also radiate lower down and around the front of the pelvis, and occasionally into the groin. If the stone is irritating the lining of the kidney or ureter (which connects the kidney to the bladder), then one may notice some blood in the urine. Kidney stones can certainly develop in a man in his 30s, but the risk of developing stones does go up with age.
To help determine if you have a kidney stone, your doctor
can conduct a more thorough medical history and physical exam to help rule out other causes of back pain. The urine can be analyzed for microscopic hematuria (the presence of red blood cells). Imaging with either ultrasound
or CT scanning can help visualize the stone and let your doctor know where in the urinary tract it is located and how big it is. Depending on the size and location, a treatment plan can be discussed. Generally stones that are larger than 6 mm may need some form of intervention (such as shockwave therapy), and those that are smaller usually pass with increased fluid intake +/- the use of medications to help move them along.
Since the cause of your back pain is not clear and you are not getting relief with Ibuprofen, it is advised that you consult with your primary care doctor
for further workup.