Thank you for providing additional info.
The most likely cause of your bump under the skin of penis is sebaceous cyst.Sebaceous cysts are not dangerous and can usually be ignored.
Another possibility is of folliculitis
.It is inflammation of one or more hair follicles.The damaged follicles are then infected with the bacteria staphylococcus.
Placing a warm moist cloth (compress) over the area may help the cyst drain and heal.Because sebaceous cysts are generally harmless and cause no pain, they may require no treatment.Only if they become painful,there is need of antibiotic & anti inflammatory medication.
if still the bump persists,then you need tests like Fine needle aspiration cytology (FNAC).In this technique, a thin, hollow needle is inserted into the mass/lump to extract cells that will be examined under a microscope.Based on this the exact diagnosis can be made & hence the treatment.
So for confirmation,I advice you to make an appointment with your doctor to have these tests done so as to know the exact underlying cause & then treatment will be done accordingly.
Hope this helped.
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Thank you XXXXX