It depends of the speed of a train. Last time I wrote on joke "how far is the train", but it made a relief in me.
It depends on 2 factors, your structure, and speed of the train.
With its speed of 150km/h I can tell you was somehow painful later, at the moment nothing because your body and wound are hot/warm, when everything cools after some hours you feel the pains. I had nothing broken, my luck. I went conscious again after some 2-5 seconds, and on my feet. Was flying some 20 meters from the hit.
More dangerous is hit from a motorbike, because it hits you at one place and not full body, and you may die.
Or more dangerous from that is some martial arts fighter to hit you with 1-2 tons of force or speed of 150-190 km/h at one place, more than 95% of people would die from that.
Of course, train moving with 400-500 km/h would be more than deadly, no "what is like" because nothing exists after.
If I know the next hit, I would wear metal knights armor, trust me.