Hi.. Thanks for the query.. Black spots on tongue can be due to black hairy tongue that occurs due to accumulation of debris and dead cells over the tongue papillae.. It can also be due to intake of bismuth containing medication. This condition is known as black hairy tongue. Other cause can be deposits of melanin pigmentation.. Sore tender tongue is appearing to be due to inflammation of tongue that can be due to either continuous trauma with sharp tooth or can be due to Infection over tongue.. So for confirmation consult an Oral Physician and get evaluated.. For now start gargling with Magic mouthwash that contains numbing agent as well as antifungal and antiseptic components.. Use a tongue cleaner to gently clean the tongue.. Do warm saline gargles.. Take Vitamin B complex supplement daily.. Take soft diet and non irritant foods.. Hope this helps.. Regards..