It seems that the dark brown lesion you have on chest may be sebaceous cyst.
It is also called epithelioid cyst
It contains cheesy material.
There may be secondary bacterial infection.
Take antibiotics and anti inflammatory drugs for 1 to 2 weeks.
After clearance of infection, it may be surgically excised under local anaesthesia.
For that, you consult dermatologist
You do not worry, you may be alright.
I hope you got my answer.
Dr. Ilyas Patel MD