Tylenol is highly toxic to cats and I don't suggest this at all.
What I want to suggest you try is diluting tea with water and giving him about a 1/2 teaspoon of this every 6 hours.
Tea has amazing benefits at improving the mouth ulcers and sores in cats and has worked better than pain medication on our patients in the hospital.
Have you found the reason why he has the ulcers?
May be decade teeth
It could be that the tooth is painful so make sure that the tea is warm but not hot as it would be less painful.
There are a number of serious health issues that can cause oral ulcers and I have to recommend an evaluation as soon as possible okay?
So, make the tea bag as normal. Then add cool water to cool the tea down.
Thank you very much but the problem is how to feed him. He is very stubborn cat . Local vet suggested to apply Gingivitis medicine but I could not because whenever I tried he scratch me very badly.Do not know how to feed the tea.Thank you