The chapter you need to analyse and study is chapter nine, which focuses on Pip's return from his first visit to Satis House and the massive curiosity with which he is greeted by his sister. Even though Pip does choose to lie, if we examine this chapter carefully, we can see that he lies out of good motives and as a result of the massive pressure he is placed under to come up with a story that is interesting and will satisfy the insatiable curiosity of his sister. Note the following quote:
I felt convinced that if I described Miss Havisham's as my eyes had seen it, I should not be understood. Not only that, but I felt convinced that Miss Havisham too would not be understood; and although she was perfectly incomprehensible to me, I entertained an impression that there would be something coarse and treacherous in my dragging her as she really was (to say nothing of Estella) before the contemplation of Mrs. Joe.
Pip therefore finds himself filled with a fear of both being misunderstood himself, but also having his words twisted so as to create an unfavourable impression of others. He therefore feels that his only option is to lie. Note however that this reveals his innate goodness as a character. He is an innocent, but one who is aware of the faults of his elders, and the way that his words, said in complete innocence, could be twisted and misconstrued to have a bad impact on others.