Does it pose a problem if you said a Bracha for seperating the Challah, when you did not need to?

If there isn't the right amount of dough to fulfill the Mitzva of Hafrashat Challah (there are a couple opinions on the exact amount which is needed), one should not recite the Bracha for it is am Isur of "Bracha Le'Vatala". one should always learn the Halachot of the Mitzvot before fulfilling them. Shabbat Shalom, Rabbi Binyamin Bamberger