Use a small amount of epoxy resin. Very strong stuff. Fill the thread with candle wax and dig it out after the resin has dried. Resin will not stick to wax and therefore keep your thread clean. If you don't want to buy a resin and hardener for such a small repair I would suggest any of the industrial strength adhesives from the local hardware store. By the sounds of it you could well do more harm than good if you were to try and remove it. Leave it in place and just stick it down.