The secret to performance, and don't be fooled public speaking is a performance, is practice, practice, practice. But, the absolute #1 thing you cannot do is stop. The show must go on even if you make a mistake. Most of the time the audience won't even know a mistake was made as long as you resist the urge to stop and correct yourself. Being able to keep the flow going in the midst of a mistake comes with lots of practice.
I'm sure you will do fine. Relax, deep breathes and if all else fails, just forget about the audience; we are always our own worst critics anyway.