Injury to a Nail
Fingernails and toenails are often injured when the fingers or toes are smashed, bashed, or crushed. These injuries usually aren't serious but may be very painful.
You can relieve the throbbing and pain caused by bleeding under the
nail by draining the blood 
from under the nail. If you don't
feel confident or comfortable doing this at home, a doctor can do
it for you.
You may have a more serious injury to your finger or toe if draining blood from under the nail does not give you immediate pain relief. You may require medical care.
Diabetes, peripheral arterial disease, and an immune system problem can cause reduced blood flow and loss of feeling in the feet. An untreated nail injury can lead to infection, foot ulcers, and other serious problems.
WebMD Medical Reference from Healthwise
