Brief Answer:
Bacterimia / Lymph nodes / cysts (hidradenitis)

Detailed Answer:
Hi.
Thanks for your query, albeit short and specific.

Noted your history of having sore throat and tiredness otherwise feeling good.
Also noted your main concern about the sudden appearance of pain under both the armpits and you can feel that the lymph nodes are hard and swollen.

The commonest cause is obviously a focus of infection somewhere in the body, which in your case could have been infection in the throat which has spread via blood as bacterimia and caught by the axillary lymph nodes.

I would advise you in such a situation the following:
Get the blood tested for infection, blood culture and sensitivity helps.
Clinical evaluation and examination by a Doctor to see that the swollen lumps are lymph nodes or cysts like hidradenitis ?
Get started on proper antibiotic, anti-inflammatory and supportive medicines as advised by your Doctor.

I hope this answer helps you and please feel free to ask further relevant queries if you need to or if you feel that there is a gap of communication.

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Brief Answer:
Cancers are painless to start with and have longer history ...

Detailed Answer:
Thanks for your feedback, read and understood your concerns.
Fatigue obviously might have been due to the infection.
Specific infection can be said about only after investigations like blood culture or so.
I can understand how one feels once you get such a result on online search such as
lymphoma and cancer.
These do not appear overnight. You have such a short history that considering these as diagnosis is remote.
Secondly you have painful lumps and the lymphoma and cancers are always painless to start with.
So please do not worry about these at the moment.

I hope this answers your query.

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