8 days post dental implant on bone graft #31, I'm still in pain, no swelling or nerve damage. What is going on?

Hi there. I would recommend you give it a few more days and see if the symptoms settle. Some patients do get unexpected symptoms that do resolve, although for the most part dental implant placement causes minimal post operative discomfort. If it does not resolve, it is possible that the bone grafted area looks good radiographically (looks like "dense bone" on x-rays), but there may be remnants of dormant inflammatory tissue in there that became symptomatic only after an implant was placed. I recommend you return to your dentist in a few days for further review, if the discomfort does not fully settle. 
What type of bone graft material was used? Was there a previous dental infection in the area that the graft was placed into?
*This is general advice only and does not constitute a professional medical or dental opinion. A full professional assessment is required.