hopping can loosen the cranks, especially when you have a square taper setup.
If you put some locktite on the bolt and tighten it up again it might be OK but but the crank might be wrecked.
If it comes loose really quickly then your crank is wrecked from riding with it loose.
You can get replacements pretty cheep on UDC. I have found that aluminum ones seem to last longer then steel but you need to tighten them a few times when they are new to get them properly seated on your hub.
I do have a square taper on em. They seemed to tighten up nicely when I put them back on (the only thing is I dont know how tight they should be)
I rode around on it after i tightened it. Everything seemed good - it didn’t loosen or wobble at all (i wasn’t jumping), so hopefully nothing is messed up.
It’s my first uni, and i’m not all familiar with maintenance on bikes or unis. So no… I didn’t tighten them when i got it, and no, I didn’t check the tightness over the first few days of owning it. I’ll remember that for next time.