Does a Small Thread on the Skin Prevent the Validity of Wudu?

If a person during wudhu , checked to see if his/her skin has any barrier and found a thread from cloth , is the wudhu valid , the person is certain that he/she used to left hand to use the cloth for wiping the fingers but after washing the face , when checked , it was somewhere in the corner of the palm of right hand , she / he thinks when washing the jawbone it might have transferred and is most likely she/he wiped the jawbone multiple time but most likely only used fingers to wipe it and is not sure how the thread might have transferred. What should be done during the wudhu . If the person did not do anything a nd completed the wudhu without removing the thread and after wudhu remebers and don't know what should be done .