tbh it really varies between shots? there have been a few times where it just hurt like the dickens but that was usually my own fault for tensing my leg or not pushing the needle through with a swift motion and instead hesitating, etc.
in general it shouldn’t and doesn’t hurt though. i mean, yes, it’s a needle, but you are putting it through a very fat area of your body so at most it should sting for a second or two. i try to practice the z track injection because it helps with not having the testosterone leak out after you withdraw the needle and also makes it less likely you’ll get a bruise, swelling, etc. you can check out how to do it here. it’s my understanding that most healthcare professionals use this injection technique for intramuscular injections so if you’re going to have a nurse do the shots for you then there’s no need to worry yourself with that.
i also really recommend taking a hot shower or a bath before you do your shot. someone on tumblr recommended this to me maybe six or seven months ago and it really does help because your skin gets a lot softer and you are usually feeling relaxed so it’s easier to do the shot.
on the whole it does get easier though because you’ve gotten used to it and there’s something nice about the whole routine of it.
anyways, i wish you luck in your transition, anon!