hyperpigmentation on the base of glans(glands) penis

I am 29 and I have a pigmented area right below the corona of the glans (glands) penis. it is only on the left side of the glans (glands) and is brown with different shades. it is flat to the touch and asymptomatic. I have noticed this about 2-3 years ago and I think it got bigger but not darker. I dry masturbate frequently and currently uncircumsized. is that a factor to why it's dark? I read that penile melanosis can result from excessive friction/trauma to the mucosa membrane and cause inflammation which in turn causes the body to respond with increased melanin production. I don't use any chemicals on that part of my body when i shower, mainly just wash with water. also have pictures if needed.