Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concerns..
As per your complain a painful lump in the armpit can be due to causes like Hair
follicle infection or Folliculitus,
abscess, bacterial infection [ Staph infection], swollen
lymph node etc.
As it is painful and just present since 4 days it looks more to be an infection and not any serious cause like Malignancy..
I would suggest you to consult a General Physician and get evaluated and he can advise you a course of antibiotics like
Augmentin, anti-inflammatory painkillers like
Ibuprofen and cool compresses over the lump..
In case if it does not resolve in a week then a Biopsy/FNAC can help in further evaluation and treatment can be planned accordingly..
As of now you can take Ibuprofen to relieve pain and also start doing cool compresses for reducing inflammation and pain..
Maintain a good hygiene and keep the armpit dry and clean to prevent further spread of infection..
Hope this information helps..
Thanks and regards.
Dr.Honey Nandwani Arora.