Stomatitis isn't a diagnosis, it's barely even a symptom, it just means "mouth inflammation".
Magic Mouthwash is another vague term, a concotion that could contain any number of things. Nystatin(anti-fungal), diphenhydramine(Benadryl), lidocaine(anesthetic) and any number of other 'potions'. Depends on the pharmacist.
My guess would be you have transient lingual papillitis, known here in the South as "lie bumps".
It's swollen taste buds. It's annoying and even painful but otherwise harmless.