Why does Jennings say he liked having a black eye?

At the orphanage, Butch, the resident bully, is shooting his big mouth off again. He's taunting Mark over his stuffed toy, making him feel like a big baby. Jennings desperately wants to punch Butch right in the face, but Mark has always told him that if he ignores him, the bully will probably go away. Yet this doesn't happen, and so Butch's mean verbal harangue continues. Mark is clearly very hurt; Jennings can see that just by looking at him. Mark trudges slowly off to bed, dejected.
This is the last straw for Jennings. He jumps on Butch's back and starts punching him. A full-blown fight ensues, during which Jennings gets a black eye for his trouble. Although feeling more than a little sore, Jennings is kind of proud of his shiner. It's a badge of pride, a sign that he had the guts to stand up to a bully.