If i was on the second day of my period and my boyfriend ejaculated on my hand and i later got up to put a tampon in, should i take plan b?

Plan B: Well sperm start dying fairly quickly in dry air and only can survive in a moist environment. You're probably fine since tampons are usually inside a plastic or cardboard tube. Also, if you washed your hands after your partner ejaculated the sperm should have been washed off. Certainly you could take plan B, but its not likely needed here.