Did you back stitch the ends? If you did, you might have enough thread to tie and bury the ends if you carefully unpick the stitches.
If you don't have enough thread to tie, I would try a sample in an hidden spot. Drop a bit of fray check on the stitching line (on both sides) where you want your thread to end. Wait for that one spot to completely dry and unpick the two or three stitches up to the fray check and clip. See if they hold before doing any more.They don't look bad with the thread colour being close, I would probably leave them alone.