You've done SOME damage, but probably not a great deal of damage. You've shortened your battery life somewhat by contributing to its sulfation.
Some irreversible sulfation is inevitable in lead-acid batteries. Some is reversible, some is not. The deeper a (lead-acid) battery is discharged, the greater the amount of irreversible sulfation.
Part of the problem is that lead sulfates are fragile, and drop away from the plates, building up as conductive sludge at the bottom of the battery. If it builds up high (deep) enough, it'll short-circuit one cell and your nominal 12V battery will irreversibly become a nominal 10V battery.
The chargers that claim to remove sulfation have some limited capability of doing so, but not to any great degree. I see them as a waste of money - they may increase the battery's expected service life of seven years to eight. Or to seven and a half. More likely, if used often, they'll overcharge a battery and result in boiling off some of the liquid that you can no longer replace because your battery now has no refill caps. In the old days, we could add distilled water or battery acid, whichever was lacking at the time (depending upon the charge state), and adjust the battery's specific gravity to ideal at the fully charged state. We even had the capability of washing the sludge out of the bottom of the battery, if we were adventurous. Yes, I've done it. Now you have fewer items on your menu - you've traded your freedom for security.
Tomorrow, provided your drove your car for some fairly decent distance today to recharge your battery, your car should start normally... unless it was already in its last six weeks of life. Doubtful. Someday you'll need to replace it - that day will be earlier than it could have been, because of your discharge, but you probably won't notice. You probably won't even remember this event by that time.