IMO, the gauge of the needle doesnt affect post injection soreness too bad, but what it does is affect the pain of injection. Larger needles just hurt more going in, but I feel like once the injection is over it doesnt matter so much.
For the past year or so Ive been getting monthly phlebotomies and they use an 18 gauge needle right in my vein! Now that sucker hurts going in, but once its pulled out it doesnt seem to hurt anymore than a 23 gauge like I use for my weekly TRT injections.