You are probably more at risk eating the meat than from anything the insect would bring. Of course, that depends on the environment. Flies have a very short life cycle. If you live near open sewers, back yards with dog excrement, etc. the fly could contaminate the meat.
OTOH, the meat could have been just as contaminated by your own hands, temperatures in the room, someone in the room sneezing...
Growing up on the farm, we ate lots of food that we would shoo the flies off of. So, just seeing a fly on a piece of meat doesn't come anywhere close to grossing me out.....