To dislodge is to remove something. When you're choking, you need to dislodge the food from your throat.
When you dislodge, you're moving something from its current position. When sumo wrestlers are going at it, they're trying to dislodge each other from their original positions. Anytime something is stuck and you want it out, it needs to be dislodged. When you're choking, food is lodged in your windpipe. That's a time when you need to dislodge quickly!