Hi.. Thanks for the query.. I have gone through your query and can understand your concern.. As per your complain Modafinil can cause dry mouth that in turn can cause thinning of mucous membranes and inflammation in mouth and cause soreness and burnt feeling inside the mouth leading to Apthous Stomatitis.. I would suggest you to consult your treating Physician and get evaluated and a thorough clinical evaluation has to be done.. In case if the symptoms are occurring due to Modafinil then dose reduction or change in drug can help.. As of now to relieve the symptoms you can gargle with numbing mouthwash containing Lignocaine.. You can start taking Vitamin B complex daily.. You can do soda bicarb gargles, suck ice pops and drink plenty of cool water.. You should chew sugar free chewing gums to stimulate saliva flow.. Avoid spicy and hard foods and take a soft and bland diet.. Hope your query is resolved.. Regards.