Yes kayleigh I heard that too on gardeners world, but when my son was about 8 yrs old he got a huge blackthorn in the side of his foot.
The dr told me just to leave it because it will come out when its ready that there was no concern, believe it or not it did come out but it was 19 months later
and very messy, infected and very painful
So maybe there not so good to be planted where children play
sheila