Since you had ringing in your ears after the concert was over, you most likely did do some permanent damage, though your hearing may seem to you to “get back to normal” in the near future. (That may not be your hearing returning to normal, if that happens, as much as it is your brain adjusting to the slightly reduced input. What’s different seems normal to you again.) The best way to enhance the healing process in the near term is to avoid more loud sounds while your hearing is recovering.
What’s permanently done from that concert is done. The most important thing now is to resolve not to keep repeating that experience. Repeated exposure to sound at volumes louder than 90 dB definitely increases your chances of needing hearing aids in middle age if not sooner, as many of us (including me) on this board know all too well. Sitting in the cheap seats far back from the stage but also wearing earplugs can allow you to still enjoy live music. Foam earplugs rated at -25 to -30dB are cheap and are best, but these will make the sound seem muffled and give a full-ear feeling that some people strongly dislike. For $10 on amazon, you can get a pair of Etymotic earplugs that are more comfortable but reduce sound by 20 dB. They do change the frequency response of the sound somewhat, but to a lesser degree than foam earplugs. I keep a pair of Etymotics attached to my keyring, so I don’t forget them–some come with a case designed for that. Audiologists can also supply custom made earplugs at a higher price that musicians like to use for even less change to the frequency response curve. It’s important to read the packaging and learn to insert all earplugs correctly to get the rated benefit. (You don’t get the rated protection if you just push them into your ear.)