Ever consider the anatomy of a dog’s neck? You have a thyroid, trachea, esophagus, lymph nodes, artery, vein, and cervical vertebra. Damage any of those and you could be looking not only a hefty vet bill, but you will likely have a dog in pain. Pain = not so great behavior = makes the behavior you were jerking the leash for worse
Contrary to the belief of some, leash jerks are not a viable option for training. Leash jerks are not conducive to training appropriate behavior, your timing had better be supernatural, behavior often gets worse, and you can cause extreme physical and psychological damage to the dog. For some dogs, being jerked on leash escalates the behavior you were trying to correct OR suppresses the behavior until Fido has had enough and perhaps enacts his frustration up the leash towards you or the other dog with you.