Blurry edges of close up photos

[pemu1]

When taking close up(4-5 cm) photos I've noticed that the edges of the lens blur photos.

https://imgur.com/a/KVdgHRb

https://imgur.com/a/bnxIPxv

This is especially visible when I take close up photos of text, letters, numbers etc.

Is it something to worry about?

 

[sitlet]

Nope, that's how lenses work.

 

[pemu1]

Nope, that's how lenses work.

Thanks for answer.