That Hurt

Warforged have a 25% chance to ignore sneak attacks and crits due to their partial construct nature. I rolled for each, and you got both. So 9 hp of damage is only the regular plus the sneak. You also did crit, which you need to roll now as well. Roll a d6 and add 1.5 x your Str mod again.

Once I know damage I'll be able to tell you what happens next. Smart use of the action point. (How many do you have left?)