Hello @Bloodshot_pico and Welcome to the forum
An easy way would be to get some brushes from the web, like from Brusheezy if you can't draw the marks with the brush tool yourself.
How to install Brushes.
1. Draw your scratches by hand, or by using custom brushes.
2. Keep the white background unchecked - for keeping transparency.
3. Use the Magic wand on Global to 'select' the black marks and invert (Ctrl + I)
4. Use white for an inner shadow - the plugin for that is found here.
5. Deselect and apply Gaussian Blur.
6. Save this in .png form. Close PDN.
7. Reopen Paint.net and import any image.
8. Import the claw marks, which will appear on a new layer.
9. Play with the layer blend modes, or color balance, to get something you like.
I hope this will work for you. Drawing the claw marks would be a lot simpler than learning to use Brushes, if you have not done so before