probably a nerve or something in the neck... when you floor it w/t that much torque it's going to jerk and pinch the nerve in your neck, but for sure call the Dr.. Until then get someone to drive you around...
2008 M3 Sedan + catless + Tune
2012 CLS63 AMG
2014 M6 Coupe + catless + KW V3
2015 Porsche GT3