I had one back in April, worst pain I have ever had. I was told as long as it passed I could continue to fly on my current medical. There are a few test results that I have to take to my next medical in order for them to issue it. If you are a member of AOPA, they will help you out.
I have a history of stones. I got a first class medical no problem. The FAA sends you a letter, telling you not to fly if you are having problems due to your stones. I have heard that you might have to get some tests proving that the stones are gone.