Why does the inside of my big toe joint itch a lot?

Fungal infection. Perhaps this is a fungal infection of the toes. Is the itching worse after wearing socks & shoes for several hours? Is it worse at the end of the day (assuming you work daytime hours)? Any redness, irritation, peeling skin? It doesn't have to have a foul odor. If yes to most of these questions, consider a fungal infection. Try some otc remedies first. If no improvement, see a podiatrist.
Big toe itch. This sounds like athlete's foot . Try over the counter topical medication like lotrimin or Lamisil (terbinafine) . If it does not improve see a podiatrist. Good luck !