I am not a medical professional qualified to give advice, but I can tell you what I know. I worked with lidocaine when I would put in arterial catheters.
I would Push it in barely below the surface, figure “halfway” through the skin, and slowly pull back on the syringe making sure I wasn’t in a blood vessel. Could seriously harm. See here
Then slowly inject it making a welt, and letting that slowly absorb. A significant portion will be numb and you can kinda spread out from there with less burning.
Depending on the area needed, I cant imagine needing more than a ml or two. I think I worked with 3% though. Or 2%.
Edit: just saw ring finger. Shouldn’t need much really. .5 ml maybe. I plan to do the same when I self install a feeling magnet.