I am surprised you have not received a multitude of well informed and other replies yet, lol.....
Mine certainly belongs into the latter
I don't have a Catamaran
and have not had an issue along these lines. And I was not there at your mishap. However, if you have no hull
damage as such and were able to sail happily home then I would suggest you may not have a huge problem long term.
As you mentioned it was a grounding and not a solid sharp impact, hence no external damage.
I am guessing it was a grounding on one side. Catamarans purely through design and build would have reasonable flex. And obviously this is the cause of your internal ribs becoming damaged, although you did not specify the damage.
I would be inclined just to contact someone who has professional knowledge of cats and repair, pay them for a few hours to inspect and advise you without telling them that you may or may not want them to repair. Then make a realistic estimation yourself out of that. If the thing tracked home okay and has no external visible damage you may well be able to repair it yourself .