Ryan has pleaded not guilty to unlawfully using a mobile phone from Wheatfield Prison on September 3, 2007, and to two counts of arson at Ms Finn's home in Dublin the next day.
Dublin Circuit Criminal Court heard evidence that Ryan complained that he was given a packet of sun cream instead of the piles treatment cream and that he told the nurse that he hoped she died of cancer.
Ms Finn told the court that when she gave Ryan the Anusol box on September 2, 2007, he was very agitated.
She said he said "give me the f***ing cream" and snapped the box off her. She said he walked off and said: "I hope you die of cancer".
She said she made a complaint which resulted in Ryan being brought to the then prison governor Seamus Creamer for a disciplinary hearing.
Mr Creamer, who is now retired, said that Ryan appeared agitated when he met him. He told the court that Ryan said he was suffering from piles and had being waiting for a number of hours to see a nurse.
He told Mr Creamer that a box for a tube of Anusol haemorrhoid cream given to him by Ms Finn actually contained a sachet of sun cream.
He said Ryan then produced the Anusol box and a sachet of Ambre Solaire sun cream.
He said Ryan said he knew where the nurse lived and gave her address.
On the following night Ms Finn was asleep at home when her elderly mother, who lives in the house with her, woke her up to say her car was on fire.
Ms Finn gave evidence that the fire destroyed both her car and her mother's Nissan Micra and the front of their home was damaged by smoke. She said she was left terrified in her own home after the alleged attack.
She added that she had taken the Anusol box from a locked pharmacy room in the prison and that it was sealed when she gave it to the accused. She said that she had never dealt with Ryan before this incident.
Ryan denies the charges and the trial continues before Judge Patrick McCartan.