For this to pop i have done the following:
-enter the room
-sit down and activate the tablet
-turn around and grab the axe,put it on the table
-go into the bathroom,change the camera angle,open the broken mirror closet on the wall and grab the disinfectant,put it on the table
-go to the window with the climate control,there's a piece of wood lying on the ground for you to bite into,when you hack of your finger later (probably not needed,but i picked it up anyway),put it on the table
-next to the entrance to the kitchen you will find a metal rod lying on the ground,pick it up
-go into the kitchen,turn on the stove and heat up the metal rod,put it on the table,when you are finished
-go back into the kitchen,there's a flask in one of the cabinets,grab it and put it on the table
You should have about three minutes left to get your finger cut off now.
-take a sip or more from the flask (i took only one)
-put the piece of wood in your mouth
-grab the disinfectant and pour it over your finger
-grab the axe and hack off your pinkie
-as soon as you have control back grab the metal rod and cauterize your halved pinkie
-get your "reward"
Trophy unlocks at the next game save a few seconds later.
That is,what i have done to unlock it anyways,should work just the same when you do it as described by me.