If I am getting fillers for the first time, is it really okay to inject just a tiny amount?

Lately, the corners of my mouth look a little sunken, and I feel like I look tired.

That area stands out more in photos than it usually does when I look in the mirror, so I am looking into fillers.

Now that I'm actually about to do it, I'm a little scared of something getting into my face.

I'm not sure if it would be okay to put in just a very small amount and observe the results, rather than filling it up as much as I want from the start.

I'm worried that if I put in too little, it won't have much effect, so I might end up having to do it again.