It may be possible that the prior injury may have led to the numbness, or that any back injury can contribute.
Imaging the back with an MRI can determine whether a herniated disk is responsible.
If negative, you can consider a neurology referral for possible EMG testing, looking for peripheral nerve damage.
If there is concern about a low foot temperature, you may want to ensure there is no vascular compromise. Your personal physician can determine if the pulses in the foot are adequate.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
It can be SIJD too. Very common disorder but very poorly understood. Many doctors don't even believe such a disorder exists!