I know a lot of gentiles who have noses that are a bit on the bigger side. The sermon on how to identify a jew says clearly that these traits can be found in gentiles as well - and that one should thread carefully when they assume a person is jewish. Just like there are quite a few jews who look like gentiles, unfortunately.
As other SS members have said, it depends a lot on the energy as well and on the whole physique, instead of taking into consideration just one aspect of it.
There have been enemy attacks on members, making them think they are jewish because they have a bit of a bigger nose.