There should be no damage at all. The tolerances are quite high. The difference between the low and max marks on the dipstick equate to nothing more than 1ltr. So, if you are slightly below the the 'low' mark you still have plenty of oil in the engine - don't worry, just top it up - but, don't over fill it!!
I find that cars that are run in properly, don't tend to use oil at as high a rate as cars that are thrashed from day 1.
Oil consumption rates of 1ltr per 1000miles are within BMW tolerance, although, if my X5 was using oil at that rate I'd soon get rid of it!
My new X5 has used less than 0.5ltr (dip stick now shows half way between low and high) over the last 5500 miles - but then I did run it in properly.