If I were to remove one of the lumbar vertebrae (The vertebrae between the rib cage and pelvis)......
I know what a lumbar vertebra is. I've taken Medical Anatomy and college medical terminology classes.
Personally, I would aim straight for the Medulla Oblongata. Take that out and they stop breathing, no heart rate, no ATP production.
Instant death.
On topic: I am still going to say no using mage hand to directly harm someone inwardly.
Remove their feet, or at least trip them with a stick
If only bone could burn
Technically, bone can burn. A lot of heat is needed. It smells disgusting when the osteocytes break down though.
Using mage hand on a twig would work, but the odds of tripping are minimal.
Can I just
try to sneak away
Sneak: 8. You attempt to sneak away, but another skeleton comes out from behind the trees and catches you. He is now watching your backs to make sure no one else tries to escape.