I had to get out of my seat to chase away a fly.
Where were you when you did that?
I was with a friend having a pretty deep conversation and I felt the fly land on my ear.
That must have been really annoying, and probably quite startling. Having something buzzing around you ear is annoying, especially if it then lands there. Trying to get rid of annoyances is only natural.
I got up to get a paper to hit it away.
I'm sure that it was a bit embarrassing at the time to have to interrupt the conversation, but surely your friend must have understood what was happening. It sounds like you dealt with the problem effectively, in the end.