Propagating bouganvillea from seed is very challenging, and it certainly won't happen with chucking a few petals into dirt. As it says in the comments you're growing weeds.
The usual methods are by taking cuttings or by air layering.
I have several happy looking bougainvilleas in my garden, but I never found any flowers that have developed seedpods. This is quite common among bougainvilleas. Here is an info page on how to grow Bougainvillea from seeds: https://m.wikihow.com/Grow-Bougainvillea It is easier to propagate from cuttings. Here is how to do it: https://homeguides.sfgate.com/can-root-bougainvillea-61773.html