Pain During Implant Placement: Reasons?

Authors

I placed an implant, MIS 6.0x10mmm, in area #19. The case was treatment planned based on CBVT scans which showed adequate width and length for implant placement. On my final osteotomy drill, the patient felt pain. I gave more anesthesia and the pain went away. I was able to finish and place the implant with good primary stability. I did not lay a full thickness flap, but instead used a hole punch because I had the CBVT scan and knew I had plenty of space. Prior to placing implant I checked osteotomy with a probe to ensure that I had bone all the way around and no perforations. My question is: why did the patient feet pain? I gave an inferior alveolar nerve block and local infiltration and he seemed sufficiently numb. Could there have been some accessory nerve ?