Explain the event of the second appearance of the ghost in the canterville chase?

The ghost appeared for the second time on a Sunday night. The family heard a loud crash after they had gone to bed. They saw the ghost sitting on a chair, rubbing his knee. A suit of armour had fallen on the ground and its weight had made him hurt his knee. The ghost growled and passed through the twins like mist when they started shooting peas at him. He blew out their candle and laughed his most horrible laugh to frighten them. Instead of getting scared, Mrs Otis offered him a bottle of medicine saying he was not well.