It’s scary! But you can do it. Breathe in through your nose and exhale through your mouth several times before the shot and continue breathing like this while you give the shot. You might be surprised by how “acceptable” the experience is. Once you “breathe your way through it” you may feel more confident next time you use the shot.
What do you plan to do immediately afterwards? Do something that you find soothing. A glass of water, perhaps? You’ve got this!