we are in the hebrew month of nisan

During the entire month of Nisan, we can rightfully say, "Chodesh Tov" since according to the Torah, the entire month has the status of Rosh Chodesh. The Torah states,  "This month will be to you the head of all months, 'Rosh Chodeshim.'" This means the entire month has all of the special qualities normally present only on Rosh Chodesh itself, a day of profound renewal and festivity.