I've had this hard spot under my gums behind my back molar for some time, but have just noticed an opening with something appearing to be in it. Could this be my wisdom tooth? I'm 23 and have not had them removed. Or could it be an absess of some sort? It isn't painful by itself, but if I jut out my lower jaw and scrape the mysterious sore against my top back molar, it does feel like I'm scraping a wound. Help and/or advice would be much appreciated!