Is your tongue sensitive on the red area? or on any other area?
Do you have any cough or sore throat now?
Do you have cracks or sores at the corners of your lips?
Are you anemic now? Do you know your hemoglobin level?
Anemia or vitamin b deficiency would have caused the entire tongue to become sensitive and reddish.
I suspect that what you have is either an inflamed taste bud - possibly as a result of a bite or a small blister or sore on the tip of the tongue.
While taking supplements will help, it will be better if you use a mouthwash containing chlorhexidine, available OTC. This is an oral antiseptic.
You need to also get a test to see if you have herpes infection (HSV1).
I hope this helps.
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Please see a dentist - you should get more help.