Depends on where you put it. When I've given IM injections, the triceps is the standard and especially the one that has your dominant hand cause using your arm helps with the soreness. I've done thigh and butt, thigh is nice and big and walking probably helps. Butt is a nice easy spot without any major vessels for an emergency (also the easiest for smaller uncooperative kids).
IM are always thick and viscous, not sure why but every IM med I've ever given it's thick. Soreness means you put it in the right spot, if you want walk around a bit today and tomorrow. Usually they're sorer the day after than the same day.
