My dad kissed my cheek today and i noticed afterwards he had a small scab of a remaining cold sore on his lip. i asked my mom and she said he had it for over a week and that im fine. im wondering what my risk of exposure was. i suffer from ocd?

You should be fine by the following reasons: cold sores are mainly due to HSV-1, a common viral infection and you might already get it (up to half of the national population gets infected at least once in their lifetime); second, his lesion was more than one week so viral shedding is less likely; and third, if your cheek skin is intact, the virus can't get in even if lesion is actively shedding.