Hello, aphthous ulcers can be very painful but usually are a sign of either vitamin deficiency or stress. The ulcers can occur anywhere in the mouth / under the tongue. Please check your haemoglobin, iron, vitamin B12 and vitamin D levels. Also, work on reducing the stress levels. Next time you see such multiple ulcers, please get it checked by an ENT specialist, as sometimes it can be due to certain viral infections also.