There is an obligation to recite the entire Hallel during the Shaharit service on each of the eight days of Hanukah. This obligation applies to both individuals praying privately, as well as to congregations praying together in the synagogue.
Before one begins the actual recitation of Hallel he recites an introductory Beracha. The text of this Beracha, according to the practice of the Sepharadim, is "Baruch Ata Hashem Elokenu Melech Ha'olam Asher Kideshanu Be'misvotav Ve'sivanu Ligmor Et Ha'hallel." This text differs slightly from the text recited by the Ashkenazim, who conclude this Beracha with the words "Likro Et Ha'hallel" ("to read the Hallel"), rather than "Ligmor Et Ha'hallel" ("to complete the Hallel").
If one mistakenly recited "Likro Et Ha'hallel," must he repeat the Beracha?
Hacham Ovadia Yosef addresses this question in his work Hazon Ovadia (Laws of Hanukah, p. 209), and rules that a person in such a case is not required to repeat the Beracha. He notes that the Maharam of Rotenberg (Rabbi Meir Ben Baruch, Germany, 1215-1293) held that it is actually preferable to recite the text of "Likro Et Ha'hallel." If one recites "Ligmor Et Ha'hallel," which means "to complete the Hallel," and he mistakenly omits a word from the Hallel recitation, then the Beracha that he recited would thus be rendered a "Beracha Le'vatala" (Beracha recited in vain). The Maharam therefore preferred reciting "Likro Et Ha'hallel" so that the Beracha would remain valid even in the event that somebody mistakenly omits a word. Hacham Ovadia contends that although Sephardic custom does not follow this view of the Maharam, nevertheless one who did recite "Likro" may, after the fact, rely on this position and thus is not required to repeat the Beracha.
If a person began reciting Hallel without reciting a Beracha at all, and realized this mistake at some point during Hallel, should he recite the Beracha at that point?
Hacham Ovadia (ibid.) rules that one should, in fact, recite the Beracha at the point where he realized his mistake. Even though the phrase "Ligmor Et Ha'hallel" is generally understood to mean "to complete the Hallel," and in this case the individual will not complete the entire Hallel after reciting the Beracha, he should nevertheless recite this text. As Hacham Ovadia cites, the Hida (Rabbi Haim Yosef David Azulai, 1724-1807), in his work Birke Yosef (683), claims that the word "Ligmor" can also mean "to read." In Masechet Berachot (9b), for example, the Gemara speaks of the custom to recite Shema immediately before sunrise, and refers to the Shema recitation with the term "Gomerim." Thus, the text of "Ligmor" is appropriate even if one recites the Beracha after having already recited part of the Hallel.
After reciting the Hallel, one recites the Beracha of "Yehalelucha," which concludes with "Baruch Ata Hashem Melech Mehulal Ba'tishbahot."
If one mistakenly recited Hallel on Hanukah "Be'dilug," meaning, omitting the sections that are omitted on Rosh Hodesh, he must repeat the Hallel but does not recite the introductory or concluding Beracha.
Are women included in the obligation to recite Hallel on Hanukah?
With regard to the obligation of the Hanukah candles, the Sages teach that since the Hanukah miracle affected both men and women alike ("Af Hen Hayu B'oto Ha'nes"), the obligation likewise includes men and women. As for Hallel, however, it appears that this recitation was instituted only for men. The Rambam (Rabbi Moshe Maimonides, Spain-Egypt, 1135-1204), in Hilchot Hanukah (3:12), writes that if a man is unable to recite the Hallel by himself, he can fulfill his obligation by listening to a woman reciting Hallel and repeating each word after her. Clearly, the Rambam felt that a man does not fulfill his obligation of Hallel by simply listening to a woman's recitation. Presumably, this is because women are not included in the obligation of Hallel. Hacham Ovadia Yosef (Hazon Ovadia – Laws of Hanukah, p. 213) thus rules that women are not required to recite Hallel on Hanukah. A woman who nevertheless wishes to recite Hallel may certainly do so, though without reciting a Beracha.
Summary: Before reciting Hallel one recites the Beracha "Ligmor Et Ha'hallel." One who recited the text "Likro Et Ha'hallel" does not repeat the Beracha. If one remembered during Hallel that he had not recited a Beracha at all, he should recite the Beracha of "Ligmor Et Ha'hallel" at the point where he realized his mistake. If one recited Hallel on Hanukah and mistakenly omitted the sections that are omitted on Rosh Hodesh, he should repeat the Hallel without a Berachah. Women are not obligated to recite Hallel on Hanukah; a woman who wishes to recite Hallel may do so, but without a Beracha.