To expand my previous comment into an answer: you refer to some sheet music as the sheet music, which is quite recommendable for pieces of most composers (to a degree - there are lots of pieces of which there are earlier versions, transcriptions, simplifications, etc.).
But, in case of Chopin (and lots of his contemporaries) this is not the right way to approach the sheet music. For starters, at first Chopin became famous not as a composer, but as an improvising pianist1. He even improvised for the monarch then ruling Poland. He became enormously famous in Poland at a quite young age, some critics even going as far as saying Chopin were the new Mozart, without a similar career just because he had not been born in Western Europe.
Of course, later he started to write down music. I can think of various reasons; some people asked him to do so, he was a piano teacher and wrote pieces for his pupils, and it was expected from him by the contemporary musical establishment. Yet, what he wrote down was not the one and only "right" "composer approved" version. As I noted in my comment already, he often produced multiple versions with different ornamentation and dynamics (or even larger differences), for different pupils (with different skill levels) or different publishers. For some/most2 pieces there are multiple manuscripts, each of which is equally valid.
The most important reason there are so many (differing) sources, compared to, say, Mozart or Bach, is that the musical culture was very much focused on improvisation instead of composition. If a melody recurred in a piece, it was expected of the performer to add an (improvised) ornament, for example. Also, many performers simply improvised everything (like Chopin in the beginning of his career; I suppose he didn't suddenly stop improvising, but I can't back this up).
The way Chopin composed his music is relevant too (not unrelated to previous paragraph); he improvised at the piano and then wrote it down. When we compare this to Bach, who thought about every individual note before writing it down, producing infinitely more complex (not to be confused with better) pieces than Chopin did, it is quite clear why with Bach the manuscript is far more authoritative than with Chopin. This is the difference between the intellectual versus the emotional, which is - IMHO - a neat definition of the difference between their respective era's, baroque and romanticism, with classicism somewhere in between.3
Lastly, I'd like to recommend the website of the Polish National Chopin Institute4. It has a wealth of information on Chopin, including free recordings of a considerable part of Chopin's oeuvre (possibly everything, I can't find a list, so I don't know how to check) by reputable (gross understatement) pianists and an astoundingly detailed biography5. This is the most prominent source for this answer.
1: some interesting and moving stories about this are found in the first section(s) of the Chopin biography on the official website of the Polish National Chopin Insitute.
2: Sorry, I have no numbers on this. If you know more about it, please let me know.
3: Fun fact: Chopin studied (granted, like almost every major composer) the works of Bach.
4: Note the tiny menu on the right hand side of the main content. You need it to switch from the site with information about the institute to the one with information about Chopin, the Chopin competition, the Festival, and the Museum. (The site on Chopin himself is of course the most recommended. The festival and the museum are great too, but that information is only relevant if you can visit Warsaw.)
5: Note: there is a biographical text which is available only in Polish (curses), but there is also a somewhat dry list of chronologically sorted biographical facts about Chopin that is translated to English (which is what I linked to).