He hasn't been the type lately to tip his hand and show exactly what he was capable of. There were only a handful of people on the ship that did know--at least, he presumed Ezri Dax did, since she was from the future, and well after he'd been outed.

"You're favoring your right side, breathing impaired--punctured lung, at a guess, likely from broken ribs considering how your ribcage seems to be a touch lopsided. You're pale and sweating, pointing towards internal bleeding. Not to mention the lacerations and burns. And may I also mention your heartbeat's been picking up, that's another sign of internal bleeding that should be checked out before you keel over."

Seriously, do not be stubborn about this, Julian had someone threaten to kill him his second shift in, he's not exactly intimidated or impressed by people saying they're tough.