Tried intermittent fasting for about a month due to reading health benefits. however, now read its not good for anyone with gallstones. i have one stone. i will no longer do the fasting but did i create damage by doing for a month?

I do not think so.

Gallstones are ticking time bombs. When you consume fat, two hours later, the food enters the small intestine and signals the gallbladder to contract, adding bile to digest the fat. A stone sitting at the outlet can block the outlet, causing pain and nausea, but if it moves into the duct, it's a disaster. If you have symptoms, see a surgeon about removing the gallbladder.