Wow , so my suggestion stop doing practice on yourself, get a fake hand. I say this from experience 😉 , Also try to keep the products away from your skin so it can calm down. It looks as if improper filing of the thumb also. Use a crayon on a raw egg and color it everywhere, then use a nail file ( not electric ) to remove color it will teach you how to file.
As to the flare up , try some Epsom salt Soak no fragrance and solar oil after. Hth