For.a while now on my left foot the side where my big toe is it has been numb there's no pain?

Check for swelling: Numbness is the first sign if you have tissue swelling called lymphedema - check whether foot is swollen - swelling could be because of minor cuts or injury.

Joplin's Neruoma: What you are describing is entrapment of the medial planter proper digital nerve which innervates your big toe. If you have a bunion on the side of your foot this is mostly what is causing it. You need to see a podiatrist. There are injections along with orthotics and shoe modification that can help with this condition. Later on it my cause a lot of burning sensation and discomfort if left alone.

There are many: Possible causes. Nutritional deficiency, side effects of medication, small nerve fiber disease, nerve compression, low back issues, some systemic diseases like diabetes can cause this as well. I would recommend you see a doctor to help differentiate which of the above it can be.