I agree completely with JGF.
And JGF....I agree completely with your PM! ;0)
Probably a habit you have developed. We cannot diagnose you on the forum but what you have to decide is if this is a behavior you can live with on a daily basis. If it is, then no need to worry. However, if you are obsessing about your tongue biting to the point that your day revolves around it, then you would need to see a psychologist to help you with it.