It certainly sounds to me as if the "coloured patch" is indeed your frænulum (given that it is the under-part of your foreskin), and your friends have given you very sage advice to simply stretch your foreskin and frænulum.
We have indeed explained all the details on this before in this forum, so please do some extensive
reading back through the forum pages, and I suggest you read every
thread on a number of index pages (each index page lists ten threads, you see) because the discussion does not always "stick" to the original title and there are many things here about your penis and how it works in relation to sex that you might need to know if not now, then later.
There's a bit to read, but it's easy enough. In fact you can sit and read whilst doing the stretching - now there's an idea! I am presuming you are looking at the Internet somewhere private because most people do despite the "safe browsing" recommendations which say that young people should always be "supervised" by having the computer in a "public area" such as the lounge-room or family room!
Anyway, it should all be really interesting; you can get the ideas about sorting out your present situation, how to properly
and effectively stretch, which is probably not quite what you have been doing so far.
I'm not sure exactly what material it was that came loose back when you were 13 or 14, it may well have been some variant of "smegma" but I can tell you - it really doesn't matter. There is no reason to imagine that your anatomy is anything other than perfectly normal
and when you have it properly stretched by doing the "exercises" we have described in the previous threads here, your penis will look just like all the ones in the "standard" pictures.
I wish someone would fix the silly statement "If stretching the frenulum fails, as it usually does" on the next page
of the article Jim cites! This is entirely inconsistent with the remainder of that site.
I know it's a "crib" from another site, but it is blatantly misleading and likely to discourage people. The truth is simply that stretching works if it is performed with a reasonable degree of diligence.