Will a seed stuck in my molar cause decay?

Lately I've been buying this passion fruit yogurt, and some bits from the seeds have gotten stuck in two of my molars. I know that the dark spots I'm seeing aren't cavities, because I've had problems in the past with poppy seeds and raspberry seeds getting stuck in these exact same spots. It usually takes a lot of work to get them out with a toothpick, and with the passion fruit seeds its been a real struggle and I haven't been able to lodge them out. I've been brushing twice a day but that hasn't done the trick either. If I can't get them out soon will it eventually cause decay and lead to a cavity?