Brief Answer:
Dead tissue accumulated under the skin.

Detailed Answer:
Hello,

Thank you for using Healthcaremagic to post your health query.
I read carefully your question and reviewed your photo.

It is a blackhead, which means that the hair follicle there has been infected and it has accumulated pus/dead cells underneath the skin and has not managed to drain. So it has created a small cyst. The pain is because of the inflammation of tissues around the small cyst and the pressure within the walls of the collection.

It will need some time, but it will gradually reabsorb from within or drain. You can only apply some hot compresses on top of it to help it reorganize and drain.
Do not try to pop it of it will get worse.

I can reassure you that it is not a cancer or something dangerous if it is what you were worried about.
If at some point it gets bigger, more painful even without touching it and inflamed, it may need surgical draining, so you might need to see a local doctor who can do a small incision in your skin and make the draining easily.

Hope this is helpful.
Let me know if you need more clarifications.

Regards,     
Dr. Papaqako

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