In short, you've only recently begun to pull back your foreskin. Why is that, by the way - what was stopping you before?
But the fact is, if you haven't
been pulling it back before, of course it's going to be a "tight fit". And the solution to that is quite simply - do it - frequently.
I'm actually not too sure how many doctors can give you a sensible
answer anyway about how to "stretch" it - I figure it would be fun to find out, but it's something more appropriate to a research organisation, and which you wouldn't care to waste your money finding out, even if you were sensible enough to tell good from bad advice and not get yourself unnecessarily worried in the process.
As to the dark colour, I suggest you go take a look at foreskin.org
for a few pictures, all perfectly normal
, some of which might
just "ring a bell" with what you are describing. In general however, you need to take note of two things - it doesn't hurt, and I shall presume that it is symmetrical - exactly the same, or very similar on both sides - which would be most consistent with natural pigmentation.
A second "check" point here - you appear to have noted your fraenulum, which ties the underneath of the meatus (pee hole) into the foreskin. Again, take note of the pictures, especially number 11 (too dark, unfortunately). Now if you have not retracted until just recently, you definitely would expect
this to be a little short/ tight, because it hasn't had
to stretch before. Nevertheless, it will accommodate, though it might be as well to do the stretch
Jim suggests for a few minutes, a few times a day.
A third point - I trust you can
really see the whole
of your glans, that is, the complete "corona" or rim at the back of the glans as per the pictures?
Look, at your age, and for some things, there is
a tendency to discover apparent oddities and wonder if you are "normal" (or more accurately, "OK" - sometimes you can actually be better
than "normal"). Guys worry about their penis, girls worry about their breasts, both worry whether there is some reason which will mean they will be infertile (the actual chance of this, is about 1 in 20!), but really as long as the shape is pretty normal, such things as shades of colour are not a problem - in fact, more of a "distinction" - a pretty feature (think: girls' nipples!).
Now we mention it, it is relatively common even for whites to have pigmentation on "rubbing" areas of the genitals, such as the cleft of the buttocks, the (inner) labia, the cleft of the groin on each side, the tip of the foreskin (which - note - is a very close match for a woman's inner labia in any case) and less commonly, various others. Do not fret on that account.
Jim is being somewhat provocative in mentioning methods of masturbation. As you must have realised, having a foreskin that does not retract really does facilitate masturbation - the sliding skin is held in exactly the right place and is truly "self-lubricating" and the pre-ejaculatory lubricating fluid ("pre-cum") is retained by the foreskin as well. That latter is a very important function of the foreskin during sexual intercourse. You will note your glans to be very sensitive, even quite uncomfortable to touch without lubricant.
That is indeed as it should be, more sensitive than someone used to frequent retraction, and much
more sensitive than someone who has lost their foreskin. As a means of masturbation, you should find that careful stroking which causes the foreskin to retract and re-cover the glans will be particularly pleasurable, and this is
in itself an amusing and acceptable means to stretch your foreskin. You need to remember to pull it forward again when you finish, failure to do so is the only
likely way for you to get it "stuck" behind the glans and difficult to pull forward; something of which ("paraphimosis") you may have read fearful stories; but even then, the solution is no more or less than to pull it forward again with determination.
In practice, I advise you to make a point of pulling it back every time you pee (urinate), and simply "playing" with it frequently , even if that does not strictly constitute masturbation.
Wash only with clean water, no soap (it's done fine so far, after all), and do read a few of the "threads" here for more formal concepts of "stretching" that you might wish to try, but it sounds as if you really are just developing normally. If you do
have further specific questions, you are welcome to ask, but you really will figure out most things by reading up in general here.