I agree with plantakiss. It looks like a pellet of ozmocote fertiliser. It may not neccesarily been in the vft pot originaly, it could have got there via another plant. If its not fertiliser, then my second guess would be some kind of egg. Its not a seed, its far to spherical and smooth. I would remove it and destroy it to be on the safe side. Its not going to cause your plant any harm then.