Thank you for consulting Healthcare Magic I can assure you a mouth ulcer which developed following trauma which fails to heal is unlikely to be a cancerous growth. But I d like to know whether you have any chewing habits. The difficulty in healing could be due to decreased oral hygiene or vitamin deficiencies. As a treating physician I d advice my patients to maintain proper oral hygiene by brushing the teeth more frequently, even after each meals; till the ulcer heals. I d also advice you to take some over the counter Multivitamin Tablets. Triamcinolone ointment can also be tried to make the healing faster. If still it fails to heal after a week consult a dental specialist and make sure no uneven teeth is repeatedly causing trauma. Thank you. Please revert with further details.