Running out of oil is never good and the top end of the engine suffers the most - if the crankshaft is roller bearing, it probably was not hurt - if the crankshaft main or rod bearing is a plain bearing, I would advise running it til it quits and install a new or rebuilt motor or you could have your engine rebuilt now to head off inevitable failure because it will fail at the worst moment (5 miles into the boonies when you are by yourself and no phone service).