Since at least the 1662 Prayer Book, Psalm 67 has been an alternative option to the Nunc dimittis – the second canticle in Evening Prayer. When Thomas Cranmer first compiled the Prayer Book, he telescoped the 7-fold daily monastic office into two: Morning and Evening, so that anyone could pray them. The service of Evening Prayer thus ended up with the traditional Vespers (evening) canticle: the Magnificat, and the traditional Compline (night) canticle: the Nunc Dimittis. He then appointed a psalm as an alternative to each canticle, usually with the express purpose of standing in for the canticle when the text of the canticle is found in one the day’s lessons.
Modern Prayer Books, however, following popular Anglican devotion since the beginning, bring Compline back as a minor office, and the Nunc dimittis is therefore a dual resident: it lives both in Evening Prayer and in Compline. If you regularly pray both Evening Prayer and Compline most days, then it may be a good idea to substitute the Nunc for a different canticle, as I’ve suggested before here.
However, today may not be the day to do that. Psalm 67 is the typical replacement for the Nunc through the majority of the year, but tonight Psalm 67 is one of the regular psalms at Evening Prayer. So unless you want to say Psalm 67 twice in the same office tonight, perhaps it’s best you don’t use it as a canticle today!