I have had mine go numb for 1 to 6 months after a big trip. Fortunately, they have always returned to normal. Most likely cause is some kind of compression from your footwear - could be caused by hiking at higher elevation than you are accustomed, longer distances, heavier loads, more brutal terrain, etc. I had to find shoes/boots with a larger toe box, and although I travel with much lighter loads than I used to, before a major trip I still train the same way I did 20 years ago - I'll work up to carrying 60 lbs for 10-12 miles. If I can survive that with no blisters or numbness I'm ready.
Also, I have read that B12 supplementation is helpful in repairing the nerves, but I have not tried this before. But, if it ever happens again, I will. In some circles this is called "Christmas Toe". You go on a summer or early fall hike and can't feel your toes until Xmas. In my case, this has been fairly accurate.