My Project is crash looping

I’ve been working on my game for a few days but today it froze so I ended the task. Now it can’t load and is showing this error. Any help?

Assertion failed: !bOnlyOneRootAllowed || (((BoneIndex == 0) && (BoneInfo.ParentIndex == INDEX_NONE)) || ((BoneIndex > 0) && RawRefBoneInfo.IsValidIndex(BoneInfo.ParentIndex) && (BoneInfo.ParentIndex < BoneIndex))) [File:D:\Build++UE4\Sync\Engine\Source\Runtime\Engine\Public\ReferenceSkeleton.h] [Line: 203]