It hasn't happened to me personally, but I have seen pictures and actual injuries/wounds from carbon arrows shattering about 6-8" from the nock and impaling through the shooters bow hand and wrist. The carbon splinters and shatters as it goes through and little slivers stay in the skin and muscle, much like fiberglass, and can cause infection and alot of pain. IMO it isn't worth the risk and I would toss the arrow. Arrows are much cheaper than your hospital bills would be.

edit: Found a pic.....