Having a pack of Dilos is a good way to combat one early on: they can slow it down with their spit attack, they can be generally hard for it to consistently hit, and carnos focus more on dinos than humans so if you get ambushed chances are it might change focus to your dilos. It can be possible to kill a carno with just 2 dilos if they can take a hit and you provide cover fire with any ranged option.
You just need a couple trank arrows, at least about nine, maybe some hide armor, and then climb up onto a rock that he can’t get up onto, then shoot him or something to Agro him, and once he comes to the base of the rock and attempts to kill you, shoot him with the tranks. Then when he tries to run away, just jump down and chase him. But make sure he doesn’t get KOed in water.