No idea regarding numbness and I had my abdomen cut open, didn’t experience any.
in regard to skin erosion, heavily smear ilex protectant pasts around your stoma, over/on top of the damaged skin, whether broken or not and apply your convex flange over it.
Leave the ilex paste on until it peels off by itself, during the next appliance change.
I found, that within 2 to 3 days, my eroded and festering skin around the stoma had completely healed, although I continued to apply the ilex paste (as a precaution), until takedown but didn’t apply it so heavily.
At the time, I used ConvaTec mouldable flanges; made all the difference, not having to cut out the hole; I also used Salts Stoma Collars, which help direct the output away from the skin.