What does Acts 22:17 mean?

Paul stands accused of bringing a Gentile into the temple. This was not only a capital offense against the Mosaic law, but it also defiled a religious structure, which was a capital offense against the Roman law. Paul did not bring a Gentile into the temple. However, he did travel to and within Jerusalem with several Gentiles. He is trying to explain to a mob on the temple mount why he travels with Gentiles (Acts 21:27–40).

He started by recounting his youth when he studied under the Pharisee rabbi Gamaliel. Paul valued the law so much that when a mob murdered Stephen for his faith, he approved of their actions and watched their coats (Acts 7:54–60; 22:20). He then earned authorization from the Sanhedrin to arrest Jewish Jesus-followers in Judea and abroad and bring them to trial and possibly execution (Acts 8:1–3; 9:1–2; 26:10).

It was on one such excursion that Paul met Jesus. He accepted Jesus' offer of salvation in Damascus, far north of Jerusalem, and spent time in Arabia (Acts 9:3–22; Galatians 1:17). When he finally returned to Jerusalem, the disciples refused to meet with him, thinking he wanted to arrest them. Finally, Barnabas agreed to listen to his story and subsequently vouched for his changed heart. Paul being Paul, he immediately started preaching about Jesus in Jerusalem to the point the Hellenists—Jews who adopted Greek culture—sought to kill him. The disciples realized Paul was a problem no matter which side he was on and sent him home to Tarsus (Acts 9:26–30).

Here, Paul gives details about his stay in Jerusalem after his conversion. While praying in the temple, Jesus warned him Jerusalem was too dangerous; his mission field would be outside of Judea, in the territories of the Gentiles (Acts229:18–21; 22:18, 21). In the original account, Jesus told Ananias that He chose Paul to share His story with the Gentiles (Acts 9:15); there's no contradiction if Jesus gave the same message to two different men years apart.