Take the bobbin out and see if it has thread dangling from it. Cut that off if it does.
Also, check to see if your plastic bobbin is rough around the edges. Throw it away if it is, and use another bobbin.
The plastic bobbin basket can become damaged. Pull it out and see if it has burrs or punctures. Gently polish them down with a very fine sandpaper (about 400 to 500 grit).