I dunno if this is right but on my cottorless cranks, they always used to come loose. Then we got two blocks of wood on either side of the cranks and hit the top one with a hammer to push the crank onto the taper thingy. Do it for both sides. Problem solvered for me, they dont come loose any more. If im wrong dont do it.
If it’s an ally crank you’re very unlikely to have damaged the hub (because the crank is so much softer). Have a look at the inside of the square taper hole in the crank - if it doesn’t look bad then just refit it and see how it goes. If it’s damaged it’ll come loose again - in that case you’ll need a new crank.
Square taper cranks do go on slightly further each time you refit them because they deform a bit when they’re tightened up (especially ally ones). Eventually it’ll get to the point when the bolt tightens against the axle rather than the crank and it’s impossible to tighten it up properly - then you need to replace the crank. I wouldn’t worry about that as long as it can still be done up tightly and doesn’t keep coming loose.
Don’t worry about the hub anyway - you’re almost certainly not going to have damaged it with a loose ally crank.
If you rode for some distance with a loose crank, I’d worry more about whether you’ve damaged your knee.
I rode several miles with a loose crank 13 years ago. I still get occasional knee problems on long rides as a result. Also, I wasn’t able to get the crank to stay properly tight for any length of time after that until I replaced both the hub and the cranks.
If you’ve caused any damage to either your crank or your axle, my guess is you’ll find out fairly soon when the crank keeps on coming loose. If that happens, you’ll need to replace both. Putting a knackered crank on a new axle will damage your new axle, and vice versa.
If your aluminum cranks are Doteks or some other crank made from one of the softer aluminum alloys it is unlikely that your hub has been damaged. Kookas are made from 7075-T6 aluminum which is among the hardest of the aluminum alloys. They may have a chance of marring or deforming your axle slightly but it is still unlikely. The best thing is that you are taking cranks off and putting them on again. If you keep it up you may turn out to be one of our most knowledgeable unicycle maintenance gurus.
Very rarely (i.e. once) I damaged a crank which worked very loose indeed. A crank that works a bit loose won’t usually cause a problem. If it does, it will be the soft alloy of the crank rather than the hard steel of the hub that suffers. (Note for pedants; yes, I know steel is an alloy too.)
It is unlikely that it really has gone on noticeably further.