Is it bad if a navel piercing bleeds?

Well right after the piercing is done sometimes there can be a little bleeding, rare but it does happen. If you have had the piercing for a few days this is just a reaction to bumping and cleaning and the bleeding should stop fairly quick. Remember it's a new hole so yeah bleeding could occur, once the tissue starts to knit the bleeding will stop and the piercing will heal up. Now be sure you are cleaning it well and properly, don't over clean as this can lead to further issues down the road.