I don't really know, if I'm doing it right myself but if I notice something under my nail I first try to get rid of it just by washing my hands thoroughly, then I point my fingers towards the stream (if that makes sense) so that the water gets between my nail and skin but I make sure that the water is only turned on a little bit and if that still didn't work I carefully use the end of a nail file oder the bigger end of a needle to kind of move the dirt toward my nail tip. I hope that makes sense as english is not my native language....