Hello and welcome.

Without seeing the pics, I'm just working off the "most probable answers"...
For the American coin, if it looks like "something stamped into the head", then it's probably post-mint damage, rather than an error.
For the Canadian coin, it's also post-mint damage, but of a different kind. This is what's known as a "love token" - an ordinary coin has had one side ground down flat, and somebody's initials engraved on it. Love tokens can be valuable, especially if the engraving is done well and/or the history behind the piece is known, but they're not "errors".
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis