Edit: Not very long after I made the post I found that there was a face inside the finger which caused the problem. Problem resolved.
While doing sculpting on the hands of my model I noticed that when sub-divided one part of one finger acts weird.
This is how the mesh looks normally:
And this is how it looks when multires is applied:
I’ve checked the normals and they’re fine. I checked if there were multiple vertices or if the edge loop was split. Nope.
I don’t know what causes that crease.
Any ideas?