Yup: Chingachgook is both a character and a symbol. The last "unmixed" member of the Mohican tribe, Chingachgook represents the death of a people and their way of life.
As the Mohicans are exalted as the good, upstanding, respectable Indians in the novel, this can essentially be seen as the demise of the "good" Native Americans. "Bad" Native Americans—as exemplified by Magua (sneaky, manipulative, treacherous)—are portrayed as the Native Americans of the future.
Is this totally reductive and pretty gross of Cooper to suggest? Sure is. We've discussed how creepy Cooper's obsession with "pure blood" is, and how all this talk is more than a little reminiscent of the way Voldemort, or, hey, Hitler talked.
But Cooper isn't just being gross. Remember that he was writing way back in the early 19th century, when most Native Americans were portrayed as flat-out bad. Native Americans were shown in literature of the time as the enemy on the frontier: by turns psycho killers, backwards simpletons or just one more thing to exterminate on the way to glorious Westward Expansion, as pesky as tumbleweeds or gophers.
Cooper even endows Chingachgook with this monologue:
"My tribe is the grandfather of nations, but I am an unmixed man. The blood of chiefs is in my veins, where it must stay forever. The Dutch landed, and gave my people the fire-water; they drank until the heavens and the earth seemed to meet, and they foolishly thought they had found
the Great Spirit. Then they parted with their land. Foot by foot, they were driven back from the shores, until I, that am a chief and a Sagamore, have never seen the sun shine but through the trees, and have never visited the graves of my fathers." (3.22)
It's not an understatement to say this would have been revolutionary at the time of The Last of the Mohicans' publication. In one monologue Chingachgook addresses land grabbing, the use of alcohol as a coercive tactic by white colonists, and the shrinking territory of the Mohicans. This is an out-and-out damning monologue: Cooper is saying "Hey, white men: You did some messed-up stuff. You hurt awesome men like Chingachgook here." We address this more in Chingachgook's "Character Analysis"—have a look-see.
So, again, what does Chingachgook symbolize? He's a triple threat: he represents his entire tribe, he represents the death of the so-called "Good Indian," and he represents the horrible stuff that European colonists did to Native Americans.