RewriteRule and seo friendly address

Question

So far, my website has been working on the following addresses: domain.com/item.php?id=XXXXXXXXXXXXXXX

I wanted to change to seo friendly addresses and added to htaccess

RewriteCond% {REQUEST_FILENAME}! -F
RewriteCond% {REQUEST_FILENAME}! -D
RewriteRule ^item/([^/]{14}) /item.php?id=$1 [L]

And it works great after entering the address:

domain.com/item/XXXXXXXXXXXXXXX

the content of the relevant page is displayed.

So that there would be no problem with duplicate content in the page code, I added:

<link rel = "canonical" href = "https://www.domena.com/item/XXXXXXXXXXXXXXX" />

I am only wondering that google has both url addresses indexed now. Shouldn't it be done on 301 redirects and if so, how, because in rewrite rules I'm not too strong? Thank you in advance for the hint.

I tried also writing [R=301,L] instead of [L] but then if I click address:

domain.com/item/XXXXXXXXXXXXXXX

in address field of the browser I can see:

domain.com/item.php?id=XXXXXXXXXXXXXXX

Greetings,

Mark