Sounds too high. What you describe sounds like mild nicotine poisoning...mind you,
mild. Cut back on the nic, see how around 15 mg does for you. I like these levels of nic, but only for brief periods. Chain vape these levels, and I will experience the same symptoms.
You didn't say the PV you are using, but I am guessing it is a regular-type 3.7V ecig. High nic can cause mouth sores if you vape it too long, and so can PG for some people. If lowering the nic does not solve this, I suggest trying VG juices. That solved the mouth sore issue with me, as well as the chronic dry mouth.
If you can, I would recommend providing more specific details next time, such as PV model, actual juice you are
vaping, etc. These things are important in diagnosing problems.
Good luck!