This is likely to be a bacterial infection of the throat. You would need a course of antibiotic, so you should seek an appointment with your primary care physician. The tenderness at the outside is likely due to draining lymph node which is common in these problems. The other possibilities of the diagnosis are:
1) Epstein Barr virus (EBV)-associated mononucleosis
2) Parapharyngeal space infections,
3) Peritonsillar abscess ("quinsy"), and
4) Submandibular space infection.
You would require a throat culture / swab and blood counts.
You may take Ibuprofen / Motrin and do warm saline gargles.
Vitamin C 500 mg per day would increase your body immunity and help in overcoming the infection.
Please feel free for your follow up questions.
I would be happy to assist you further, if you need any more information.
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