You are aware that the little cover comes off so you can see the whole thread track? If not, just reach down under the white plastic above the needle area and pull up carefully, it should lift straight up and reveal the take up arm. If you can snip the thread and release it, even if a little knot stays there, you can continue to sew. That little knot won't hamper anything. Also, use either dental floss or a serger chain of thread and run it through between the tension plates (only go one way, not back and forth like flossing) both sides to dislodge any little bits.