OK, I know how it sounds, but this really happened today! As is usual with boys, while changing the diaper he transformed into fountain. I tried to cover myself with my hand, which deflected the stream and a few drops got into his ear. I was told that you should not try to wash/clean internal parts of an ear of a new-born child. OTOH, I believe that humidity inside ear, hygiene, and aesthetics provide some good reasons to clean up the mess in this case. Are the acids from child's urine dangerous for ears? What should I use to clean it up?
Just a few drops of urine is entirely inconsequential. You can wipe away any wetness that is on the skin and in the outer ear, but don't do anything inside the ear canal. If it's a lot then you could wash the outer ear just like you would during bath-time, but still leave the inner ear alone.
The fresh air often encourages a bit of peeing but as I mentioned here you can avoid "rogue peeing" by covering the crotch with a washcloth when you open the diaper.
Urine is sterile leaving the bladder but doesn't stay that way for long; it is an ideal growth medium for bacteria. I would rinse it out.
There is nothing terribly wrong with getting clean water in your baby's ears. You will not get water in the inner ear (that is the third and deepest part of the ear) or the middle ear (where ear infections occur). The outer ear ends at the tympanic membrane, which will keep everything out of the middle ear. The infant's ear canal is not deep at this point, and it should be easy enough to rinse out. While you are washing the scalp/face/etc., just let some drops of clean warm water run from the outer ear into the canal. When the canal is full, turn your baby's head so that the water runs out. If it's been a while since this happened, repeat once. Dry well with a towel, again turning your baby's head so that the canal drains.
Male infants do urinate on themselves. You would wash his face if he urinated on it, wouldn't you? Same applies to the ear. No biggie. He won't get "swimmer's ear" if that's what you're afraid of. I'd be more concerned about bacteria growing in what little urine is left in the ear canal.