Suppose someone accidentally counts the wrong day of the omer after making a bracha, and then realizes later that night what he had done. How should he rectify this? Should he count the correct day with/without a bracha? Should he do something else? What if he realizes in the morning that he counted the wrong day the previous night with a bracha?
Mishna Berura 489:32: If a person makes a mistake in the counting the best option is to fix it “toch kdei dibbur” (appx 3 seconds). If too much time passes and it is the type of mistake which disqualifies the count, he should count over again and make a new Bracha.
Regarding if he realized his mistake in the morning, it would be similar to one who totally forgot to count and he would say the correct Omer without a Bracha.