These thoughts from Upsaid
"To my mind, Acts 2:38 is not even primarily addressing the question of individual sins and individual forgiveness. Peter's stunning peroration in 2:36 is that "all the house of Israel" -- very emphatically corporate! -- should know that God has made Lord and Christ this Jesus "whom you (pl.) crucified."
The command to repent and be baptized is Peter's answer to his audience's question about this horrible, nation-destroying sin of Messiah-rejection ("They were cut to the heart" and asked "What shall we do?" , 2:37). They are thinking, "Oh no. This guy that our leaders executed was actually the Messiah after all. We're screwed!"
