Hi.. Welcome to HCM.. So sorry to hear about your problem and will try my level best to resolve it to the best of my knowledge and experience.. As per your explanation it seems that you are suffering from Recurring Apthous Ulcers or Canker sores and the symptoms of burning sensation of the inside of tongue,lips and inner cheeks along with sores seems to be due to it only.. It can be due to a number of causes and as you have sinusitis,post nasal drip can cause throat and oral infection and inflammation and it can be a cause for ulcers.. Along with it if you are taking any medications like antibiotics it can also be a cause due to its side effects.. You should consult an Oral Pathologist and get evaluated and he can do a thorough examination and advise investigations like oral swab culture, blood tests to rule out the cause and treat accordingly.. As of now you can take symptomatic treatment to relieve the symptoms like gargle with numbing mouthwash containing Lignocaine, take anti inflammatory painkiller like Ibuprofen, take vitamin B complex daily,apply steroid ointment like Triamcinolone acetonide, avoid spicy and chilled foods, suck ice and gargle with cold water.. Hope this helps.. Regards..