What Causes Severe Pain And Numbness In Lower Legs And Toes?

I fell and sustained a three part fracture to the neck of my right humerus on 7/2 this year, its 3.5 months on and while my arm slowly heals I have developed terrible stinging to backs of my lower legs from knees downwards? and often stinging and numbess to my toes - what is going on? - age 50, female, 5ft 4ins height, 9stone 4 pounds weight.