Your avatar 3D model is noisy usually due to low-quality input (blurry scans/photos) or incomplete post-processing (like not denoising textures or cleaning the mesh).
Noise refers to unwanted grain, pixelation, or rough surfaces—common causes include cheap scanners, bad lighting during scanning, or skipping steps to smooth textures/mesh. For instance, a phone scan in dim light picks up random artifacts, and not denoising leaves them visible.
If you used a mobile scan app, re-scan in bright, even light. For editing, use free tools like Blender: use the "Denoise" feature for textures or the "Smooth" modifier for mesh—start with small adjustments to preserve your avatar’s shape.