Hello XXXXXXX
Thanks for posting your query.
In order to provide you with a most probable diagnosis and guidance I need to know a few details regarding your symptom which are not provided in your query.
Please provide the following details so that I can help you ,
1. The onset , duration (since days or months etc)and progress of the lesion ( yellow spots).
2. The description of size and shape, whether raised?flat? Surrounded by redness or swelling?
3.Any associated symptoms like pain,fever, swallowing difficulty , sore throat etc
4.any significant past or present medical illness and medicines taken .

That said and done , the most probable causes of such spots include aphthous stomatitis ( ulcer), oral thrush , rarely infections or malignancy.
In most cases a confirmed diagnosis requires a thorough clinical examination by your dentist or a ENT (ear nose throat) surgeon, who after confirming the cause can start appropriate treatment .
Sometimes some oral sores can present like this during periods of weakened immunity and stress , however they usually resolve on their own .
In any case if such spots persist for more than 2wks or increase in size then they should be examined by a doctor to rule out the cause .
Meanwhile following steps help in prevention and treatment of minor oral sores

Avoiding very hot foods or beverages
Reducing stress and practicing relaxation techniques like yoga or meditation
Chewing slowly
Using a soft-bristle toothbrush
Visiting your dentist right away if you have a sharp or broken tooth or misfitting dentures
Hope this information is helpful to you.
Awaiting your response,
Regards

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