What do you think Finny means when at the end of Leper's testimony, Finny calls out, "I just don't care. Never mind."

Finny is frustrated and really doesn't understand himself. Finny is contending with a lot of things in his life. He's crippled (more or less), he's got teenage angst surging through his veins, he loves gene in all kinds of ways yet resents Gene at the same time...This little trial is too much for Finny to handle hence his "I just don't Care" statement. I'm not sure what you mean by the last part. Leper always was at Devon before he went to the war.