I have a single page application, quite simple even, and I used the tags tags with% and% with%, without creating a header , as I found it unnecessary.
Is there any rule or recommendation about this? Can I use a tag section without necessarily having a footer ?
No, they are completely independent, you use each one according to your need, if you do not have a footer just do not use it.
On the other hand you could create a simple footer by placing an instruction or putting the company name, system version, something that does not leave anything.
From the technical point of view it is perfectly valid, from the point of view of design it would be interesting to have some useful information, just do not feel obligated.
