It's hard to tell from the pic, Wellington15, but the pink could be the third eyelid. No idea what else you might be seeing, but if the change has been that rapid, your dog needs to be seen by a vet. There's something very definitely wrong with his eye. If there's an infection and it's left untreated, he could lose the eye.
When you make the appointment (and it should be sooner, not later), explain to the vet how anxious your dog gets. Perhaps he can prescribe an anxiety reducer, like Alprazolam, to calm your dog for the appointment.
Good luck! Let us know what the vet says, pls!
And welcome to the board.