you need to secure your threads -- somehow--
there are a few different techniques people use-
you can do a couple back stitches at the beginning/end;
you can take a few tiny stitches at the beginning/end;
you can leave tails- thread them onto a hand needle and bury them in the sandwich;
you can leave tails, tie them into knots-then bury them....
which ever method you choose is fine- but you need to choose one of them