Yes, a tampon is not a cork, it's a sponge. Once it is full, it will start to drip and will also absorb no more. If you can't get the stuck one out, don't hesitate to go to an ob-gyn and have them get it. It is a very common thing to have to go to the gyn for, and as the previous poster mentioned, it can be very dangerous (not to mention icky) to leave one behind.
Your tampon will only be able to absorb as much as it can but after a while you'll start to leak cause there's no more room for it to absorb blood so you'll ending up staining your panties. Try to get it out as soon as you can because it can cause infections and can possible cause you to get the Toxic Shock Syndrome.