Yes that is perfectly normal. Don't try and open up any of the male flowers since the pollen isn't fully developed yet. If you have any gourd or summer squash flowers they can pollinate your pumpkin, assuming your pumpkin is a pepo (which it probably is). And don't worry many more female flowers will form on your pumpkin vine.

Are you 100% positive they didn't open already? Male flowers usually only bloom 1 day and then close forever. The bloom's best chance at pollination (either you or another pollinater) is early morning, before 10 (9's best). After that point, the flowers close and start to die. I would go out and see your flowers in the morning.