Everyone is nervous about their first competition – regardless of the sport. The key is to enjoy the experience.
Do not do a complete workout in the warmup room. The warmup room is to get warmed up and not to complete a full workout. At a recent competition, I watched a number of athletes do a complete workout in the warmup room before their opening attempt on the platform. By the time they got to the bench press they were worn out and ended up bombing out of the meet.
Plan your warmups to get you ready for the platform and then go out and have fun. Save the work out for the prep weeks.