Thank you for your query at DoctorSpring.com
You are suffering from a painful lump on left side cheek, the size decreased with medication.
There are many possibilities, correct diagnosis requires examination whether firm/ soft, size, shape and USG or MRI can be done to get more information.
But based on your description I can assure u this is not a malignancy. Because malignancy is usually painless and it 'll not decrease in size with medicine, rather it increases with time.
You tooth problem is most probably a separate disease. So for this cheek swelling u can observe for one to two weeks safely, if not improving u can do USG and can get opinion from local specialist again
Hope this helps
Dr. Sunil Jalan