My grinder with cut off wheel got me Sunday

^^^This is great advice. Also, cutoff wheels have a tendency to break and fling shrapnel (esp. cheap ones from Harbor Freight) so ALWAYS wear gloves and a face-shield (or at least safety-glasses).

If you are cutting through something, be aware the the wheel can "catch" as soon is it completely penetrates the thickness. Hold on to it tightly, and SLOWLY draw it along the seam or trail you've made, and keep making passes to evenly cut until only a thin section remains. You can then bend or break it off and use a flap disc to clean-up the cuts.

 

Glad it's not worse, OP, and glad your kid wasn't hurt. Wishing you a speedy recovery!

Yes! We used superglue on my head when that whole engine thing happened. It works!

Very good advice. It'll be less likely to "walk" and risk hurting someone if you give it a set path.