smudge

SMUDGE noun

[ C ] uk/smʌdʒ/ us
a dirty mark

пятно, клякса
a smudge of ink
smudge verb [ I,T ] uk/smʌdʒ/ us
If ink, paint, etc smudge s, or if it is smudge d, it becomes dirty or not clear because someone has touched it.

пачкать, размазывать
Be careful you don't smudge the drawing.