If it all worked out, you'd ctb instantaneously on impact. If you panic and move or a piece of the locomotive or a cowcatcher cause a glancing impact then the damage could be almost anything. Losing a limb or limbs, brain injuries if the head is impacted etc. Depending on the ground clearance of the engine you may be caught beneath it and dragged.
As far as others are concerned, shock and trauma could be expected to the loco crew, accident and emergency workers who attend and railway employees who have to clear your pieces from the track and the locomotive.