It seems that the lump in your armpit and throat problems are unrelated. You may be suffering from acute pharyngitis and may need a course of antibiotics along with supportive treatment. This medication may help reduce the size of the node in your armpit as well (the meds would act on it too). What is the size of the node? If there is no reduction in size you may need an FNAC to see what it is.
Next Steps
Please visit an ent specialist for confirmation of diagnosis and further management
Health Tips
Saline gargles and steam inhalation should help with the throat.