Hi
Based on your history and the sites you describe, you could be having cold sore like ulcers which may be completely unrelated to the extraction or could have been triggered by the trauma associated with the extraction which is unavoidable.
Have you had such ulcers before ?
Next Steps
You do have to get yourself checked with a dentist, who ll need to examine the character of the ulcers and associated history and accordingly prescribe ointments or gel for local application. You could also see an Oral Medicine specialist for further evaluation.
Health Tips
Avoid spicy foods for a few days and too hot foods as that ll cause pain / burning.