In 30+ years of Chopin studies as a musicologist I have yet to come across an attributable primary source for this, by which I mean either Chopin writing in his correspondence to this effect or a reliable source reporting it with credible circumstantial evidence as regards when it arose in conversation, in what company on what occasion etc.
If anyone of modern scholars would have picked it up, were there such a primary source, it would be Zielinski (1993), and he remains as silent as the grave on the matter.
Purely subjectively, my view is it would be utterly out of character for Chopin to have said such a thing at all, given his intimately wry view of his own output on the extraordinarily rare occasions that he would let such things slip at all. "Moje nudny nuty" (to match the Polish vernacular alliterative play on words, "my scrawly scribblings" or "my tawdry tootlings") is the very best we have got that is completely attributable and utterly in character. (1) Given Chopin's equally well attested to tortuous relationship with the act of creation itself, that too does not bode well for the likelihood of this being an attribution with merit that you cited.
Checking your exact, specific phrasing of the quote against resources online, 39 of 43 returns point, directly or indirectly, back to Wikipedia, and that attribution itself points seemingly to a publisher's blurb... :-(
Bottom line, on the primary evidence available to me, and the scholarship as a whole that I am aware of to date, he likely never said it.
All the best,
(1) Letter to Fontana, October 9th, 1841.