02 Pathfinder will not take gas?

There is a dance you can do with the accelerator pedal and a stop watch to make it blink out the error code on the SES light. Around here (Texas) most of the parts stores (AutoZone, etc.) will read the code for you if you don't want to try the blink-it-out procedure.

As far as the tank not taking gas at full flow, I would get underneath and check for damage to the filler hose (collapsed?) or to the tank itself (bashed in?). If the occurrence of the idiot light coincides with the weirdness in adding gas, it probably is an evap code, but you will have to get the code to find out.