I marvel at all these vets with ex-ray eyes that can make a diagnoses over the phone, the chances of a sting are not high, there are a few buzzers around but not many.
As he already has a soft pallet problem I would suspect he has a sore throat that a course of AB will fix I have seen Cavies walk funny when they have that viberating soft pallet attack so think that is all the walk is hope you have booked an early appointment.
If he had a fish bone caught he would gag repeatedly trying to move it.
Try a spoon of Maluka honey that should sooth his throat
Hope he is OK do let us know ((hugs to the little man))