Lost in Translation When You Are Already Fearful

Our son was sick yesterday and had a high fever. I could not get it down so we took him to the emergency room (it was after hours). Every five minutes he asked if he was going to have to get a shot.
"Myles let her put your arm band on," I said (referring to the lady who registered him).
"Is she gonna give me a shot?" he asked before offering his arm.
At this point I had to say something to relax him-
"Oh of course not. You are done with all of your shots buddy!"
When we finally get to the back to the nurse triage, he was still hesitant about things.
"Come on up here so I can get your weight," the nurse said.
He looked back at me.
"She would get in trouble to if she had a needle," I reassured him.
He finally relaxed too much once she sat down to enter information in her computer.
"Uh, you gotta back up, Myles, she doesn't need any help finding the keys."
I'm surprised she didn't say anything- he was right on her.
She went through the spill about allergies, any medicines and any concerns.
"Well, no one has ever said anything but there were a few times when he has come to the hospital and he was given albuterol and breathing treatments. I know that is for asthma right?" I asked.
"Well, his doctor would have to be the one to diagnose him," she replied.
Myles jumps on my lap and covers his face-
"The doctor is gonna dye my nose, mommy?"
Diagnose... dye his nose- I guess I can see why he thought that.