There are different kinds of salvation in Scripture. Paul spoke about the salvation of our souls (Eph. 2:8,9), but he also spoke about his physical salvation from prison (Phil. 1:19 cf. Ex. 14:13). Additionally, he advised Timothy that if he would continue in Pauline doctrine he would “save” himself from the misery that always comes from not continuing in Pauline doctrine! (I Tim. 4:16). There is also the salvation from despair that the hope of the Rapture gives (Rom. 8:23,24), and the Rapture itself is called a salvation (Rom. 13:11).
The salvation in our text is yet another kind. In the context, Paul says he made the Corinthians sorry “with a letter” (II Cor. 7:8), i.e., his first epistle to them, in which he rebuked them for not disciplining the man living in fornication (I Cor. 5). They then “sorrowed to repentance” about this (II Cor. 8:9). The wordrepentance means to have a change of mind, and they changed their mind about allowing the fornicator to continue in their midst. This “saved” them from the dangerous leavening effect that his presence would otherwise have among them, and so their godly sorrow worked repentance to salvation, a salvation Paul assured them they would not regret or repent of later.
It also worked another kind of salvation among them, one similar to the salvation Paul references in I Corinthians 5:5, where he speaks about the fornicator and tells them,
In context, we know that delivering the man to Satan meant putting him out of the assembly (v. 2,13). Letting him wallow in sin might destroy his flesh, but it would bring him back to the Lord, and “save” him from a loss of rewards at the Judgment Seat (I Cor. 3:15). The Corinthians would likewise be saved from such loss by their obedience to Paul’s instructions. Their sorrow worked this kind of repentance to salvation as well, another salvation they would not regret, of course, for no one at the Judgment Seat will ever repent of having done the right thing.