The phenomenon is called first bite syndrome. It’s from your salivary glands pushing out a large volume of saliva when you first bite into some types of foods.
When your salivary glands do this — push large amounts of saliva out — it causes pressure in the salivary ducts. This is experienced as “pain.” The location of the major salivary ducts are under the tongue and inside your cheeks around the area of the top molars. If you eat salt and vinegar chips, or dill chips, when you first bite in, you might notice this sensation.
Some describe it as a very sharp sensation — almost painful — right on their lower jaw, on the hinge of the jaw. Some describe the feeling as “burning.” The feeling seems “weird” to some people.
There is no harm being done to your body, though. And as you eat more foods that make you salivate, the feeling can be expected to generally improve.
And time might effect how strong the feeling is. If you don’t eat anything for a while, then eat something, you can make a sudden flood of saliva, which will cause the pressure “pain” feeling.
How to maximize your chances of feeling this: maybe try eating something “tart.” Acidic foods — most “tart” foods are acidic — require saliva that acts as a buffer to the acid in you digestive system.