To sum up the other comments:

Don’t worry it’s nothing.

PS: if you don’t have a professional do something about it quickly your house will explode.

That’s why I stopped asking / reading answers about this kind of stuff on forums, and have a professional come and see to give me a real advice. Every case is different and reading random advices on the internet can bring a lot of anxiety. Especially if you decide to do nothing while some people told you that it could be really bad.