Yu Ping, I have been ordering from iherb.com for years, including Jarrow B12. I recommend them. As for your pain being good at night and progressing through the day, intuitively these sounds consistent with it being related to your spinal injury. Your spine is under little to no stress while lying down, but is used and abused as we go through the day. If the pain is radiating from your spine, I believe this means the condition would be called radiculopathy, which is a neuropathy. It may also be polyradiculopathy and/or polyradiculoneuropathy. But I'm no expert on spinal injuries.
Ron