Reichu: Even through the armor, it still hurts. This is the first time we see the phenomenon of the Eva's pain being felt by the pilot, a subject I'll get back to momentarily.
HeWhoPostsStuff: Or maybe he hit his head on the front of the plug when the thing fell over?
Reichu: Well, considering the angle that the cockpit would be at after EVA-01 falls, I would have expected him to fall out of his seat entirely! The show largely seems to disregard these kinds of issues and treats the cockpit as if it is always upright, regardless of what position the Eva is in.