You really owe it to yourself to do it! I don't know where you're from but many areas have "singaround" nights which often only consist of a few regulars who've played all their best stuff there before and would love to hear someone new. You'll only need a song or two and the other players will be willing you on! Once you've broken the ice it's the best feeling in the world and you'll want to do it again. Like a lot of people, nerves are just something you need to manage and may always be a concern but it needn't stop you singing and playing in public. Don't die wondering!