The second question concerns me more than the first.
Depending on what kind of kink you’re into, “too far” can be an easy line to cross. In some relationships, it’s even expected… part of the emotional budget is set aside for just such an eventuality.
But even when “too far” is easy, talking to them about it should never be hard.
Just ask him about it. Ask if it was an accident, or something intentional that went awry. If he gets defensive or avoids the conversation, that means it’s neither… he did what he wanted to do, and wants you to shut up.
Which is your cue to go find someone who gives a damn.