MECCANIXITY 10PCS PC Dust Filter, 40mmx40mm PVC Computer Case Cooler Dustproof Mesh Cover Fan Grills for Computer Chassis Speaker, Black

Not an issue. It's just plastic. Only thing it would "damage" would be the fan but if you don't hear it moving around when you shake it, it's probably not in there. If you want to fix it, just get some dust filter mesh and glue it to the back side of that hole. Something like this would be enough.