Why does Lennie think that he might not get to tend the rabbits?

Lennie was supposed to take care of his puppy to prove that he would be able to have the rabbits. Sadly, he killed the puppy.

And Lennie said softly to the puppy, “Why do you got to get killed? You ain’t so little as mice. I didn’t bounce you hard.” He bent the pup’s head up and looked in its face, and he said to it, “Now maybe George ain’t gonna let me tend no rabbits, if he fin’s out you got killed.”