If i was in your shoes id wait for a quiet moment and get you and him alone.
Talk about the time you came onto him, tell him you regret it and you dont want to feel arkward and can you be friends.
I know it will take LOADS of guts to do it, especially if you still have a few feelings for him, but think of what the outcome will be. You will feel loads better and you can work without tip toeing around.
You gotta think you may work about 40 hours a week, thats 2080 hours a year. Do you really want to spend that many hours feeling uncomfortable????
So basicly you may have to face up to the fact that getting another job is a possiblilty.
Whatever you decide, good luck with it.