I must be totally clumsy or something because about 8 months ago I hit both of my toenails on corners of the walls and doors, so I cracked both toenails and they both fell off completely, I was wondering how long it takes a toenail to fully grow back? Is there anything to boost the growth of the toenails? Thanks in advance.

Oh my gosh! That happened to me about two years ago. I lost my big toe toenail completely! I freaked out-it looked so weird. It took two months to grow back to where no one would notice. But, by one month, I had enough toenail that it didn't looks so weird in sandals. good luck!