Earlier today I noticed a sore/blister type thing on the shaft of my penis, about where the head starts (from the shaft). From what I've figured, it only affects the skin of the penis itself and is not connected to anything else. It seemed at first like a nasty pimple or something, but it's started to swell and become a particularly nasty color (like a dark reddish, bluish, black).

It'd be much appreciated if I could put my mind at ease or something.

Is it painful? A sore is never something to ignore. Healthy genitals should be free of sores. A simple culture could determine the condition. Do seek medical advice.
lesion penis Search Results From Healthline (http://www.healthline.com/search?q1=lesion+penis&utm_medium=google&utm_source)
=symptom_search&utm_campaign=sympserp&utm_term=sore%20on%20penis

Earlier today I noticed a sore/blister type thing on the shaft of my penis, about where the head starts (from the shaft). From what I've figured, it only affects the skin of the penis itself and is not connected to anything else. It seemed at first like a nasty pimple or something, but it's started to swell and become a particularly nasty color (like a dark reddish, bluish, black).

It'd be much appreciated if I could put my mind at ease or something.
I'm seeing a doctor soon. Thank you for the link. =)
I'm fairly certain at this point, seeing where it has gone and what it has become, that it is a staph infection, probably MRSA. Very bad stuff.