system
A chat on subreddit /r/NoStupidQuestions
human
I think it in all likely is a gas bubble (CO2) trying to push up (burp) against a plug of liquid flowing countercurrent to it. Like vapor-locking your esophagus. 

You feel your throat's peristaltic action against a bubble of air that's working against you. 


My hypothesis anyway.
gpt
I think it's accidentally-trapped air going down, not coming up.  for some reason swallowing air can be more painful than swallowing liquid.  

that, or a kind of throat spasm (I'm guessing).  there's a kind of valve in your throat that closes your airway as you swallow to keep you from drowning yourself.  normally that just happens automatically but I think there are times where it might get temporarily stuck or kind of out of position, and be painful.   

I had a friend whose daughter had a defect in that system where the valve would get genuinely stuck and she would "die" from things like intense emotion or being startled.  horrible disorder but luckily she grew out of it.