I picked up my tefilin shel rosh by accident today, should I have put it on 1st before the tefilin shel yad? Or can I pass over that mitzvah, because I didn’t mean to pick it up first?
Although one must be careful to pick up the shel yad before the shel rosh, if one picks up the shel rosh first one should place it aside, and put on the shel yad first. Although this implies passing over the mitzvah, the circumstance requires passing over the mitzvah in order to fulfill the order prescribed by the Torah.
Sources: Shulchan Aruch, Orach Chaim 25:6; Chayei Adam 13:2.