You don't have to try all combinations. You can start with the most probable ones first.

For example, you can start by only assuming you made a single error. Private keys are usually encoded in base58 afaik, so every letter could have been any of these 58 characters. Generally, you could even go farther and check for "common typos" first. However, since base58 explicitly excludes letters which may be mistaken for other letters, I don't think that makes sense. There shouldn't be any common typos from reading or transcribing a private key encoded in base58.

So in your case, I would first try to change a single letter. If that doesn't work, try combinations of two letters etc.

Good luck.