Mark007, Yes it was from the acid in the pineapple.
I have had pineapple burn the corners of my mouth....never my tongue.....(yet) When we get one I eat most of it ....at one time ! More worse, once I took a tour of the Dole Pineapple factory and at the end they turned us loose to eat as much as we wanted........every laughed at me. I ate and ate and ate and would have continued to eat but the tour bus would have left me there. My mouth was very sore after wards. I love pineapple. I will probably some day have a hole in my tongue just like you. I hope that your tongue heals fast so you can eat some more! *S*
Take care and dont get salt in the hole in your tongue.
Sorry for the humor, I know it is no fun to have the "pineapple burn".
Blueduck