EMPLOYEE WENT TO CHECK ON CREW INSTALLING PINS IN TRACK PADS. WHEN HE WAS 5 - 6 FEET FROM THE CREW HE FELT A STING IN HIS LEFT CHEEK WHICH BEGAN TO BLEED. A SPLINTER OF METAL FROM THE EDGE OF THE PIN FLANGE SPLINTERED OFF AND ENBEDDED INTO HIS CHEEK. THIS CAUSED A 3/4"" CUT THAT REQUIRED STITCHES.