Why is my render noisy/blotchy? I'm new to Blender and wonder why, when I render the image, the image is noisy or blotchy.

The render result is shown below.

You can see the effect clearly at the skin area.

Can someone help me resolve this issue?
It looks like denoising artifacts due to low render samples settings.
Go to render properties tab and increase the number of render samples.

The idea is to keep the render time low and the image as good as possible. More samples will increase the render time and quality.