Found this after a puncture:



The damage sits inside the rim:



Is this unsafe to use?

I would not ride on that tire, the sidewall has a major puncture

That is interesting. I wonder how it happened. I would replace the tire.

I'd love to know, possible that I rode on the tire after the puncture too long to get off the road safely, the rim may have cut into it.

looking at the 2nd pic, the tire/rim interface shows a "wow".
Assuming you used proper care in mounting, I wouldn't use it.
Why risk possible catastrophic failure? You only have one body.

That tire must be replaced.

Check your brakes carefully; it looks like my tire when the brake was mal-adjusted and rubbed against the tire. (You might also need to true the wheel.)

I will have a look at the brakes and see if there's an issue here, ordered a new tire.

I'll look into truing the wheel.

I don't think the OP has to ask, or that we have to warn about any danger. The wall is separated from the bead for some distance, and I doubt the tire will hold full inflation pressure long enough to be ridden.

This is unrepairable damage, possibly from riding when flat or severely underinflated, or possibly from the edge or worn overhang from a worn brake shoe slowly cutting through there.

Whenever I see this kind of damage, I immediately remove the wheel and look/feel for overhang on the upper (outer to rim) shoe. If I see any, I file it off with a rasp, then reinstall the shoe lower to prevent a repeat event.

Otherwise, if nothing is found, get out the butter and jam because the tire is toast.

How big was the hole in your tire?
It looks like you had a blowout.

The problem is that the wire holds the bead in place. Without it, the bead can come up from the rim, and your tube blows out the side (then the tire may close up as if nothing happened).