Yes, that is a flower appearing. The photo in the profile isn't the best, but it was all I could find online that wasn't copyright.
The flowers are to me small versions of the houseplant calla lily, if you've ever seen that flowering. The petals will turn white, and there is the stamen inside. The flower remains underwater when the plant is submersed as it usually is in aquaria.
Plants sometimes flower shortly after you acquire them. That is usually because they have been grown emersed by the nursery, and marsh plants (many of our popular aquarium plants are not true aquatic but amphibious marsh plants) normally flower during the emersed period. I did once have Anubias flower for me after it had been in the aquarium for several years, which was a nice surprise.