Thanks for the details,
Looks like some sebaceous cyst pr Lipoamtous swelling which have superimposed infection.
Oral antibiotics like Augmentin for 5-7 days,Anti inflammatory pain killers like Advil,Diclofenac Sodium will help to reduce the size of the swelling as well.
When the inflammation subsided, surgical excision is the next treatment which is definitely required.During infection we usually avoid surgical intervention
unless there is abscess or pus collection inside.
In case you feel the swelling is fluctuant or increasing in size, there is fever,chills, it might need intravenous antibiotics, surgical incision to drain the collection.
I hope the info helps
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