Hi An_245750,
Although I cannot diagnose you online what you are describing sounds like Fissured tongue and/or Geographic tongue. Both are harmless conditions with a genetic component - so if you have siblings, children or parents nearby look in their mouths and ask if they have had similar issues with their tongue!
Geographic tongue and fissured tongue are often seen together, in fact 15% of people will have one or the other or both. Because you are describing occasional sores that come and go I would suggest that you investigate Geographic tongue first as it used to be called wandering rash of the tongue! Part of the diagnosis includes the fact that it gets better and worse.
If you have Geographic tongue it becomes uncomfortable because the tongue is exposed. If you look at the surface of your tongue you will notice small hairlike projections, filliform papilla. The filliform papilla are made of keratin (like your hair and nails) and they protect the tongue. When they fall off, like they do in Geographic tongue, the underlying surface is exposed and easily irritated. Don't worry, the will grow back but often as one area of filliform papilla grows back another falls off.
Patients with Geographic tongue report that acidic foods and spicy foods can be quite irritating.
There is no specific treatment or known etiology for Geographic or fissured tongue but you do need a confirmation of this clinical diagnosis. You do not need a biopsy. Your dentist can recommend an over the counter product or biofilm to cover the sores while you are eating.
Geographic tongue can easily be misdiagnosed as "thrush" (oral candidiasis) by clinicians unfamiliar with the condition so your dentist may be most qualified to properly assess and diagnose your tongue.
If you do not have a dentist you can look on the American Dental Educators Association website for information on Dental schools, Dental hygiene schools and hospitals with a dental residency program in your area.
I hope this helps!
Dr. Gwen Cohen Brown