First, never do a pull request from master
.
It is a branch also used in the original repo, and it should be kept in sync with upstream/master
, upstream being a reference to said original repo.
You should create a dedicated branch for the evolution you want to promote as a pull request, and push that branch to origin (your fork).
See more with this "couple of tips for Pull Requests".
If GitHub doesn't see any difference, it could because you were in a different branch , or even in a DETACHED HEAD when you did your commits.