Thanks for your query.
Its good that you had washed your hand after the weed killer spilled on your hands.This has prevented further contact & damage. Since you did not develop any itching, burning after it had spilled on your hand it is unlikely that your bowel movement is altered on second day because of weed killer.
Drink plenty of water & hydrate yourself properly.
Kindly show the mouth blister
to your family doctor to assess the severity of the blister. Maintain oral hygiene
in order to avoid infection.