Q.Will My Fairy Castle Cactus Heal Itself With Animal Bites On It.
I put my cactus plant outside one day to get some sun; when I came back home a lot of the stems were bitten off and I found some teeth holes on the main stem. I was wondering if the cactus will heal the holes up and be ok. Thank you.

Certified GKH Gardening Expert
The primary danger to your cactus is that with any wound, there's a good chance that infection or infestation will set in. You'll need to rinse the wound thoroughly with hydrogen peroxide, cut away any part of the tissue that looks rotted or darkened, and dry the area completely. You may want to dust the open areas with sulfur. Moisture of any kind is going to invite infection, so you'll need to protect the plant from water for a while. It's unfortunate that this happened in the winter because the plant will heal faster in the warm weather.
Here are two articles that may be helpful:
https://cals.arizona.edu/yavapai/anr/hort/byg/archive/cactusculture.html
https://www.gardeningknowhow.com/ornamental/cacti-succulents/fairy-castle/fairy-castle-cactus.htm