I used to be painfully shy but then I became involved with running a folk club where three of us used to take turns doing the mc'ing.
After a couple of years of standing up in front of an audience and frequently making a fool of myself the nerves certainly decreased to a point where I started to feel comfortable. So volunteer to be an occassional mc at your local club to get used to speaking to an audience. I'm sure your offer won't be turned down. And don't under any circumstances apologise for mistakes. You're doing the best you can at the time, so feel pleased when it all goes right. And after all these years I still blush!