Hello from JustAnswer.
Could you attach a picture of the lump, either a close-up picture or a high resolution image that will allow zooming?
How long has this been present?
Thank you for the picture.
This image is worrisome for a specific type of infected sore, called a chancre. A chancre can occur with a couple of different bacterial infections, including syphilis and chancroid. The chancre of syphilis typically is painless, while chancroid is typically painful. However, we usually prefer to use diagnostic tests to clarify the specific infection.
While both of these infection can be readily treated with antibiotics, there is no good method for treatment that can be done at home. Therefore, the usual approach would be to see a doctor, either your regular doctor or a doctor at a GUM clinic.
If I can provide any additional information, please let me know.
Please let me know if I can provide any further assistance.
The appearance is not the typical appearance of a sebaceous cyst, because a sebaceous cyst would usually be covered by normal skin. For a sebaceous cyst to have this appearance, it would require that you must have picked at it extensively to damage the overlying skin. However, on exam, the doctor can feel the deep skin layers, so can detect a cyst under the skin, even if the skin is damaged.
So, the image is not typical for a sebaceous cyst, but the picture cannot be a full substitute for an examination.