If you cranked up the pressure to carb faster (as you were indicating in your other thread), it could be a little bite from the CO2. Sometimes when you use that method, the CO2 will need a few days to mellow out. That kinda defeats the purpose of the quick-carbing though, right? I use set it and forget it but try searching on CO2 bite or carbonic acid bite. In the end, I'd just wait a few days and see if it mellows.