‘But Barnabas took him, and brought him to the apostles, and declared to them how he had seen the Lord in the way, and that he had spoken to him, and how at Damascus he had preached boldly in the name of Jesus.'
Then Barnabas, who all knew as a godly disciple, who had sold his field in order to support the believers in the church in Jerusalem (Acts 4:36-37), came forward, introducing Saul to the Apostles, and declaring how Saul had seen the Lord in the way, and how the Lord had spoken to him, and how at Damascus he had preached boldly in the name of Jesus. And from then on he was accepted. It would seem that Barnabas had contacts in Damascus who had brought him news of all the happenings there, while the Apostles, being more in the Hebrew Christian community, were more isolated from work outside their purview.
In Galatians Paul tells us that he saw no Apostles other than Peter, with whom he met up a period of fifteen days, meeting also with James, the Lord's brother, and no doubt discussed the things concerning the Kingly Rule of God and, we may assume, they agreed together (Galatians 1:18-19). How then is this to be reconciled with the above? The answer probably lies in the fact that ‘to the Apostles' was seen as fully satisfied by presenting him to Peter and James, the Lord's brother. Their sanction would be sufficient to satisfy the whole of the twelve. What Luke is pointing out is not that all the Apostles were there, but that Saul had the full sanction of the Apostles as a whole.
We should note in this regard the differences in emphasis between the two passages. Luke is concerned that we should see that Paul was fully accepted by the Apostolate. Paul was concerned to demonstrate that he was not dependent on the Apostles, and that the source of his revelations was God. Thus Luke is all embracing, while Paul is exact.