Once you've settled down, try to piece things together. How long were you inside the animal? Was the storm that led you to cut open the animal and crawl inside to survive a normal thunder-and-lightning type storm, or was it a nuclear-explosion-wrath-of-God-end-of-the-world type storm? Do you remember a blinding flash of light? Did you get the sense that others were being raptured?
After you've come to grips with the fact that life as you know it has ended, it's time to make a plan. Quickly assess what weapons you have on you and what weapons you can make from readily accessible resources, like ribs. Start setting traps. Practice knife throwing. Make yourself a lair. Slather yourself with dirt and look sullenly off into the distance. Allow a single tear to roll down your cheek for all the countless dead.
Now it's time for the most important question of all: are you comfortable eating human flesh? There are certainly going to be roving bands of cannibals stalking the countryside in ragtag convoys bristling with postapocalyptic weaponry, and the biggest decision you need to make is whether to join one of those bands or heroically battle against them until you are, inevitably, eaten.
I can offer little guidance on this except to say that here at COACISSW we feel that joining any group ever is a slippery slope to socialism. And the only thing worse than a postapocalyptic wasteland is a postapocalyptic wasteland full of commies. So my advice is to stay solo. Crouch a lot. Climb trees. Glare at rocks. And if you have to eat someone, eat one of the damn cannibals, because every survivalist knows eating a cannibal isn't cannibalism. It's justice.