Bottom f tongue I suppose is floor of mouth. Swelling in that region is usually swelling of submandibular salivary gland duct swelling or its opening which gets swollen. There is a relation with meals and swelling increases with meals and gradually decreases. You need to see an ENT and he/she needs to palpate the area and look for any stone in the region and investigate accordingly. If you mean base of tongue as the bottom, then it must be a taste bud or a lymphoid follicle which is swollen due to inflammation. Please use hexidine gargles thrice daily and analgesics. If it does not resolve, do see an ENT. If you are a tobacco user, stop it. regards