I suggest trying a different brand of e-liquid.
Experiment with different pg/vg ratios. You may also be over-sensitive to certain flavors.
Be sure to do good oral hygiene. Brush teeth. Consider getting a special tongue brush, too.
It's pretty well known in the community that vaping can cause
dry mouth, especially when you first start vaping. My guess is that is what is causing the inflamation on the roof of your mouth and tongue. There are products available which can help. Increase your fluid intake, chew gum or suck on hard candy to get saliva flowing.
Biotène® Dry Mouth Oral Rinse