Welcome at HCM.
I have read the complete details which you have given.YOu are having numbness
at the distribution of L4 deramtome.
This area is supplied by common peroneal nerve
.This nerves comes out from the lateral aspect of upper leg.It looks that most probably you have stretched some fibers of this nerve during your work or walking.
At present you should consult to a neurologist
.You may need a test like NCV to detect nerve function.
It looks to be a minor injury
which will heal by complete rest in a splint
or slab with knee in flexion position.You may take a nerve supplement like vitamin B COMPLEX to accelerate the healing of nerve.
Hope this will help you.
With best wishes.