Hello, I Have Severe Lower Back Pain. This Just Seems

Hello,
I have severe lower back pain. This just seems to come and go but quite often my back locks so that I'm in a stooped forward position. The pain travels down the left side of my leg into my foot and there is a swelling on the left side of my back - almost in line with my hip. The pain worsens if I remain in a position for a few minutes. Please could you give some advice.
Regards