EE WAS WORKING A TRACK OFF OF EX550. HE WAS HAMMERING IN A TRACK PIN, WHEN A SMALL PIECE OF PIN BROKE OFF AND WENT INTO HIS LEFT UPPER ANKLE. THE PIN WENT THROUGH COVERALLS, TIP OF BOOT, APPROX 11/2 INTO UPPER ANKLE. HE WAS DRIVEN THE THE ER AT NAVARO REGIONAL HOSPITAL.