I'm probably not as scared of needles as it sounds like you are, but my advice is to look away and squeeze something super hard, like a stress ball. It helps for me! And if you have someone with you, try talking about something that interests you. This might help take your mind off of the needle. And again, this might not work for you, but if that stuff doesn't help you could try looking at the needle the whole time as if it's not your arm but like you're watching a video or something. Imagine that you're trying to learn how the procedure works, not emotionally but as if you're trying to study it. This doesn't work for me at all, but other people I've talked to about this say it helps!
Meds have helped a huge amount for me. I wasn't happy with the idea that I'll basically have to take meds every day for the rest of my life, but at this point, it doesn't bug me that much. The benefits of Vyvanse greatly outweigh the drawbacks, at least in my case.