If a toenail has completely fallen off, it can take up to 18 months for it to grow back. A toenail can take longer to grow back if the nail bed has permanent damage.
In some cases, old nails do not completely fall off, and they act as a protective barrier to the nail bed until the new nail begins to grow. Throughout the growth process, it is important to keep the nail bed dry and clean to prevent infection until the nail grows back or the nail bed has hardened. It is also important to wear comfortable shoes to prevent any further damage.