hi, i'm 17. i have a dark discoloration at the bottom of the glans of my penis. it's near the frenulum and urethra opening.the discoloration had been there since i was 15 and had been less significant. however in recent days, it has become darker i also noticed a mild blister within the urethra opening. additionally, i feel no pain whatsoever, no burning when urinating, etc. i am not sexually active. i do want to know what is this phenomenon though.