I'm assuming that you've resolved the conflicts now, so that the first commit in git log is a merge commit.
Firstly, it's a good idea save where your old master branch was, just in case you want to go back. You can do that with:
git branch old-master master^
Then, if you want to reset your master branch to the version of master that you've just fetched from the origin repository, you can do that with git reset --hard:
# Make sure that you're on the master branch:
git checkout master
# Make sure the remote-tracking branches from origin are up-to-date:
git fetch origin
# Check that there's no output from "git status":
git status
# Now reset master to where origin/master points to:
git reset --hard origin/master
Note that git reset --hard is a dangerous command - it will throw away any uncommitted changes, which is why I suggest making sure that the output of git status is clean before using it.