I have studied your case.skin rash
and enlarged lymph node
[armpit swelling] suggests possibility of viral illness.
Another possibility of systemic infection leading to skin rash
You may need to investigate in form of complete blood count
, CRP, and if required fine needle aspiration cytology.
You may need clinical examination also to confirm diagnosis.
Till time you can start medication and antibiotic consulting your treating doctor.
Hope this answers your query. If you have additional questions or follow up queries then please do not hesitate in writing to us. I will be happy to answer your queries.
Wishing you good health.