The other sign of a broken bone is the sound of crepitus, although please do not go grinding at a broken bone in an effort to elicit that particular response. The primary rule of first aid is not to inflict further injury. Next you'll want to know if any blood vessels or nerves are injured. That is the area that will be affected by loss of blood flow or impairment of any nerves. Look at the colour and warmth of the affected fingers compared to the uninjured side.
Blood supplies oxygen and warmth amongst other things.
If blood flow is impaired, an area will no longer be toasty warm and pink. Capillary refill is the other test done to insure that circulation is not compromised. Pressing down on the skin and then releasing it will leave a white mark that should immediately return to the normal skin colour. What you are doing is momentarily occluding the capillaries and then allowing them to refill when you release pressure. Compare capillary refill between the injured and uninjured side.