When you use a thermometer and poke a large hole in the meat, can you use the same hole to accurately gauge temperature later on?
I use the same hole if what I am checking is large, like a loaf of bread, and I don't want to poke it full of holes...although with my instant read thermometer, the hole is not particularly large.
If the hole is a large proportion to the item (big hole in the side of a cookie...I know, absurd, but you get the idea) where you think heat can run down that tunnel you've made, then be concerned, but I can't imagine any situations where it is likely that the thermometer hole is going to let enough heat in to alter the cooking.
I CAN imagine a situation where a thermometer in place could help transmit heat to the center and make it, potentially, cook quicker. We used to put a large nail in the center of a potato that we were baking in the coals of a fire so that the steel would help transmit heat to the center of the potato to make sure it got done evenly, but I don't know how much of a difference even THAT made.
I wouldn't recommend that, most likely it will alter the results somehow.
But why do you get huge holes? My Instant Read Thermometer makes only little holes, so you don't kill your steak etc. again. When you have an older meat thermometer, most likely it is designed to stay in the oven the whole cooking time.