My cast iron has become flaky, did I damage it?
If it's flaking, it wasn't seasoned right to begin with. However it really only matters on the cooking surface. You want seasoning to build up, but it shouldn't flake.

See if it really is coming off, try with you fingernail. If it's coming off then get all of it off that you can by chipping it away. Scrape it off. If it doesn't come off then leave it alone, and season as normal another new layer.

If you aren't happy with it, you can always strip it and start over but that's usually something you end up wishing you hadn't done. You do this by putting your cast iron in the oven and running it through a cleaning cycle. Be warned, don't do this unless you already know what to do and how to season your newly bare cast iron.

Old cast iron seasoning is the best, you don't want to start over. I have some with a 1/4 inch of seasoning (I am exaggerating) on the outside of the pan and it looks crusty, but the inside seasoning and finish is baby skin smooth and slicker than any Teflon coating. I keep it that way by scrubbing lightly with a green scrubby to "tip" the bumps down before putting back in the hot stove to cook another thin layer of oil.

You can't ruin cast iron except by breaking it. Don't worry, it's not ruined, it just needs some care. Some of my best cast iron was a lump of rust I rescued from the junk store.