Hello Vitor!
Instagram outputs information about accounts in JSON format when you request it via their web API.
https://www.instagram.com/USERNAMEHERE/?__a=1
Under “profile_pic_url” or “profile_pic_url_hd”, there will be a link to the profile picture.
There might be easier ways to do this, but I have found that this is the easiest (and free) way to do it.