Flesh wound, he had a piece of bamboo or something sticking through the skin and pulled it out and wrapped it so it wouldn't bleed, just wounded, not broken.
"God's not supposed to be a hack horror writer." - In The Mouth Of Madness
I actually think they should have had Peter disappear from the movie after the creatures take him from the beach, never to be seen alive again... it would have added a lot more suspense; his subsequent later running around, only to die without any further effect on the plot, was quite superfluous IMO, and I would have prefered to never see him again until Liz found him in the cave, dead.
It was also a little confusing. At one point he encounters one of the tribesmen eating a guy on the ground. From the guy's clothing, it seems like it must be the big guy. Yet later we see him in the cave and they're about to eat him then. He's not even marked at all. But it literally couldn't have been anyone else.
That amount of blood, there should've been a bigger wound, or multiple wounds. Plus, why are they even wounding him, dragging him out to the jungle, and then just leaving him there, anyway? A prank?