I have multiple flat worts on my stomach. I have been treating most of them with a banana peel, as they are wide spread (in the morning I just spread the inside of the banana peel all over my stomach, and let it dry, then get dressed). The biggest wart I decided to treat with ACV and tape with bandages. I noticed the same thing as you describe: it's been a week now and the wart has become very "raw" and it stings, and I don't see improvement. AS a matter of fact, it seems to be getting worse, but I didn't know if it was just the 'process' before it gets better. Moreover, there are now satellite warts around the big one, which seem to have popped up in the areas where the tape was.
The banana peel is much slower, but it seems to be actually drying the warts. Ah... I have much more work... Good luck everyone.