Pip was uneasy at the end of chapter 1 because he saw a gibbet and it made him think the convict looked like the pirate come back to life.
Pip has an overactive imagination and an unhealthy since of guilt. He always worries, and always fills himself with self-blame and self-doubt. After his terrifying meeting with the convict in the churchyard, Pip’s imagination runs wild. This is why when he sees the creepy gibbet, he gets nervous. A gibbet is a place where people are hanged, so naturally a little boy would be frightened by the sight of it. The presence of the convict near it increases the effect.
On the edge of the river I could faintly make out the only two black things in all the prospect that seemed to be standing upright; one of these was the beacon by which the sailors steered… the other a gibbet, with some chains hanging to it which had once held a pirate. (ch 1)
As Pip watches the convict, he imagines he looks like the pirate brought back to life. He becomes even more frightened and runs home. Pip’s guilt at associating with the criminal, and being out alone when he is not supposed to, catches up with him.
The image of hanging the convict is actually foreshadowing, because Pip is later in the position of trying to help the convict avoid this same fate.