All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, is His slave and Messenger.
The scholars held different opinions regarding the ritual impurity (Najaasah) of vomit. The majority of the scholars held that it is ritually impure in absolute terms, but the Maaliki scholars held that it is ritually impure if the vomited food has already changed (from its original state when consumed) and is ritually pure if it has not changed. You may act upon the opinion of the Maaliki scholars to avoid hardship and inconvenience. It is not obligatory to wash the child’s face or the inside of his mouth and the like. Rather, the child’s saliva purifies his mouth, as established by Ibn Al-Qayyim in Tuhfat Al-Mawdood. It is not obligatory to purify any object unless it is known that the ritual impurity has transferred to it. Some scholars held that insignificant ritual impurity is pardoned in all cases, and this was the chosen opinion of Shaykhul-Islaam Ibn Taymiyyah . You may follow it since you suffer from OCD. It cannot be judged that the impurity has transferred to anything else except in the case of certainty. In the event of doubt, purity is the default state.
We conclude our answer with the advice that would save you from such questions and others, namely to disregard obsessive whisperings completely and pay no attention to them at all because excessive indulgence in them incurs grave evils.
Allah Knows best.