Brief Answer:
tooth infection/gum infection,medication, RCT/scaling

Detailed Answer:
Thanks for your query. I have gone through your query.
As far as The pain in the tooth is concerned, I have two possibilities. It cae be because of the tooth infection secondary to decay. The other possible cause can be a gum infection secondary to deposits over the teeth.
Nothing to be panic, consult a oral physician and get it evaluated. Mean while you can take a course of antibiotics like amoxycillin and pain killers like diclofenac (if you are not allergic). They are prescription medications.
Once the diagnosis is confirmed the tooth can be treated with either root canal treatment or scaling.
These are the possible causes, diagnosis and treatment plan based on your short description of your problem. If you can upload the images of the tooth of interest i can give you exact diagnosis and treatment plan. I hope I have answered your query. If any queries are there reply me back. Take care.

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