Hi,
If the painful blisters have healed and they have reappeared, then it might not be cancerous.
Self examination of oral cancer , articles you will find in healthfeed of Practo. Go through that and still if you have doubts, visit nearby dentist.
Next Steps
Quit tobacco habits.
Health Tips
smoking can be harmful not only for Mouth, but lungs and throat. so it is advised to discontinue the habit.