Just move on.
This one already thinks of you as beta friend-zone guy.
You think some male lion who lost a fight is just gonna just hang around pining away for some lioness who's been taken?
He's gonna move on and bulk up for the next competition.
Life is too short and there are too many other women out there to get hung up on one who likes somebody else.
Learn from your mistakes and move on.
If you can't find any potential mates, you need to expand your search area.
The best your gonna get with this one is raising that other guy's kid if things fall apart.