What is troubling Raplh and Piggy at the start of chapter 10? How do they feel?

Tired, injured, and disturbed by the previous night's action (Simon's murder)  they discuss Simon. Piggy reminds Ralph that he is still chief, or at least chief over those who are still with them. Piggy tries to stop Ralph from dwelling on Simon's murder by appealing to Ralph's reason. Piggy says that he participated in the murder because he was scared, to which Ralph replies that he was not scared. He does not know what came over him. Piggy tries to justify the death as an accident provoked by Simon's "crazy" behavior, but Ralph, clutching the conch defensively, is consumed with guilt and regret and insists that they took part in a murder.