Okay, but what about...
It's okay to be nervous! It's kinda like speaking in front of your classroom. But this is one time and place you're going to have to be brave. It's super important that you help the prosecutor and the defense and the jury know what you know to be true. This is how justice is done.
Just say "I don't know" or "I don't remember" if you don't know something. We don't want to make anything up that isn't true.
If you are asked to come up to the witness stand, you'll be asked to swear an oath. But the Bible or any other book is mostly from movies and TV. Instead, you'll just be asked to swear or affirm that you'll tell the truth, the whole truth, and nothing but the truth.
No, you are not going to jail. But court is a place where some people are sentenced to jail if they are guilty of crimes. If someone hurt you, you're in court today because a prosecutor is trying to prove to a judge and a jury that person hurt you. And it's up to the jury to decide if they're guilty. And if all that happens, the judge will decide if the person who hurt you is going to jail or some other punishment.