Some have the custom that during the Omer counting period (until the 34th day of the Omer), one does not wear a new garment which requires the recitation of the “Shehecheyanu” blessing (i.e. a new garment which causes the wearer joy, such as a new shirt and the like; however, a new garment which does not require a “Shehecheyanu” blessing, such as an undershirt and the like, may be worn during the Omer period according to all opinions). Some rule leniently and allow wearing new clothing.
Some act stringently and abstain from sewing and altering new clothes during the Omer period; however, our custom is to be lenient in this regard. Even according to those who are customarily stringent, nevertheless, if this is being done for a bride or groom who is getting married on the 34th day of the Omer, there is no custom to be stringent at all.
According to Maran Rabbeinu Ovadia Yosef zt”l, there is no reason to be stringent and abstain from reciting a “Shehecheyanu” blessing on a new fruit during the Omer counting period. Those who have observed this custom have done so in error, for they have confused this period with the “Three Weeks” prior to the Ninth of Av during which time one should not recite a “Shehecheyanu” blessing on a new fruit. However, during the Omer counting period, there is no such custom to be stringent, for the days of the Omer are not days of mourning as are the “Three Weeks” during which the destruction of the Bet Hamikdash and other tragedies occurred. It is for this reason that it is inappropriate to recite the “Shehecheyanu” blessing which translates to “Blessed is He… Who has allowed us to live, to exist, and to reach this time” about a period which is designated as a time of national tragedy. On the other hand, the period of the Omer is not considered a tragic time; on the contrary, the Ramban writes that the holiness of the days of the Omer counting is tantamount to that of Chol Hamo’ed. There is therefore no reason to act stringently in this regard.
Nonetheless, it is proper to act stringently with regards to wearing new garments during the Omer. If there is truly a necessity to wear a new garment, one should try to wear it on Shabbat in which case one may also recite the “Shehecheyanu” blessing. Similarly, one may act leniently and wear a new garment during the Omer period in honor of a Bar Mitzvah or Berit Milah celebration.