Have you ever sat in an audience and hoped the presenter would fail? Of course you haven’t. As a speaker, most members of an audience want you to succeed. They look forward to being inspired, educated or influenced. A speaker should consider the audience as a friend and not the enemy.
As a professional you have some thing of value to say. Your being in front of the room is no accident. The audience is looking forward to what you have to communicate. It is important that you spend the time needed in preparation so you give the audience what they came for.
Most audiences generally do not noticed when a speaker is nervous. For many inexperienced speakers the severity of their nervousness is more of an issue that resides in their own mind. If an audience does notice your nervousness, the value of the content they are receiving is what they are most interested in acquiring. Keep in mind that sincerity trumps style every time. As long as you give solid information, much will be overlooked. Realizing this, there may not be any reason to apologize for your nervousness. When you apologize you are bringing the audience attention where it need not be. Practice not to offer an apology when nervous.
The great orator, Winston Churchill, would purposely add a bit of nervousness and mistakes to appear more ordinary.
The audience is your friend. Treat them as such.