Welcome to Just Answer,
You most likely have a problem with the shift-interlock system. This is what keeps you from moving the shifter with out pressing the brake, but it can also cause problems with your lock cylinder.
You need to remove the center console to access the adjustment on the shift-interlock cable. Pull outward on cable locking clip to allow cable to self adjust. Press clip down to lock in place.
If it will not adjust the cable will need to be replaced, but you should be able to get the key to to turn by messing with the cable.
DO NOT switch ignitions from one car to the other. The keys are coded to the vehicle and you will have no end of trouble if you switch them.
Let me know if you need more help,