In the small toe there is a fungus but it turned into a deep opening like a wound how should it be treated?

Wound: Treat like there's an infection if a wound suddenly opened where there was a fungal infection previously. See your physician for appropriate medicaitons.

See a podiatrist: The area may need to be debrieded and then treated with an antifungal.

It is possible: If a toenail infection becomes severe enough, it could lead to loss of the nail. Toenail fungus often time cases the nail to be brittle and loose form the nail bed. The slightest amount of trauma could cause the nail to be completely detached causing loss of the entire nail. Get it taken care of by a professional to avoid preventable complications.