Hi. I Am In UK. My 20 Month Old Son's

Hi. I am in UK. My 20 month old son's thumb nail is coming off. I went to the Dr's and they suggested putting germoline on it but on reading the information leaflet it said that if it is ingested then to seek medical advice immediately. As my son is always putting his thumb in his mouth I decided not to apply this and have instead been soaking his thumb in diluted TCP antiseptic liquid. However, I can't find any information online regarding whether this is safe or not. The label does not state that it is not suitable for toddlers and babies but as I am going to be doing this for a while, I want to make absolutely sure it is safe to do so.
Thank you
Sara