Is there a specific part where the numbness starts or lingers?
Also, just to add to the stretching advice above, standing on your toes won’t fully stretch your achilles.
The stretch is to find a small step or curb and stand on the edge of it with your heels hanging over, in the air but keeping your feet horizontal. Gently lower your heels, so they are lower than your toes, while keeping your toes on the step, and go back to the horizontal. Then raise your heel above the toes, and go back to the horizontal. Be gentle and patient as it can take ages to recover from achilles damage or to make notice any improvements.
If this is the cause of your problem, then it might also be worth stretching your feet, all the back of your legs including your bum and lower back too, as these areas all work together and could help.