Hello sir, the redness can be due to multiple reasons. It can be as simple as a rough tooth surface irritating your tongue to a complicated lesion. Only a examination can tell the proper diagnosis. If it’s not painful then it can be a benign lesion, which should be treated as soon as possible. If the lesion is painful and your not able to eat, the. Try eating ice cream or cold milk shakes to calm inflammation, you can also take brufen and apply a anesthetic gel on the tongue redness