They can't hard a bone. however, with enough picking at one spot it may cause a fracture. like a chisel.
Right, these tiny almost invisible chakra blades on your fingers aren't lethal enough. They may, however, pierce a small artery or make a pinch on a larger artery. Like the karotid or the jugular, you may cause a small cut on them but not completely cut it and cause the person to bleed to death. However, if you land enough strike on the vein or the artery, they'll may be looking into some serious matters.
You may also injure joints and tendons on the person. They'll feel a small piercing sensation upon one piercing but enough damage on their biceps tendon and they'll may loose the ability to have a functional arm. Or damage their clavicle ligament and they'll lose the ability for their whole entire arm/shoulder.
I'll give you some more pointers. While you can also block the chakra flow to certain areas, you can also increase the chakra flow to areas. For example, if you strike chakra points around the heart, you'll cause a massive overflow of chakra to the ehart which causes the heart to fail for example. You can also do the reverse. Block the chakra points around the heart, causing it to fail. Opening and closing tenketsus around organs can cause the organ to fail. Hmm, alright, so you know about the major parts of the body as in both tenketsus and the lethality of the finger strikes when you want to attack the opponent internally. If you strike tenketsus around the lungs (the back of the victim) it'll cause them lung failure due to the failure of the operation of the lungs and they'll suffocate. Strike enough spots on the back of their head and make them go blind. Give me your opinion on this and also I'll ask you this. Why do you think what I just described happens like that?