I  backed into a low hanging small branch. It had a 4 foot drop and bent up a prop. I replaced the prop and got an engine obstruction warning. The props turn freely and i don't anything out of place.  I hovered it with  no issues. Any thoughts

Does it look like the arms are bent at all? You might need to perform an IMU calibration in the Go app and a sensor calibration in the Assistant 2 Software as well.