|But maybe the problem can be so small that i wont see it.|
Unless you took the fan apart, you wouldn't see it. And taking it apart might very well break it completely.
Will it do any damage if it would start doing loud noise again?
The danger is not in the noise. The danger comes from the fan seizing, which can result in overheating. It'll be difficult to detect when it seizes, because your laptop doesn't always run with active cooling.