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1.The history and symptoms suggest the possible cause will be hair
follicle infection / inflammation with collection, next could be
lymph nodal enlargement.
2.The infection can be treated with a course of antibiotics, where as the lymph nodal enlargement will occur due towny infection or inflammation any where in the body.
3.So any illness you are aware of can be treated.
4.As a remedy do not use tight shirt until complete healing, use soft clothing which will not cause the rubbing, avoid squeezing, pressing the lump - as you can complicate and disturb healing process.
5.Avoid shaving, mean while you use trimming till complete healing - that will help.
6.Apply local anti inflammatory cream with remedies explained - should be well in couple of days. Good luck.
Hope i have answered your query,
any thing to ask do not hesitate to ask.
http://doctor.healthcaremagic.com/doctors/dr-ganesh/62888