Is it true that it be haram to blow on ones good before eatin even tho it be hot to eat?
According to a fatwa from Egypt’s fatwa authority, it is not a prohibition, it is just good manners not do it since it can cause the food or saliva to fly off, and it is for this reason that the Prophet 
disliked it. It is therefore considered disliked (makrūh), not forbidden (ḥarām).
According to the the important legal theorist Shams al-Dīn al-Āmidī it is permitted to blow air on hot food to cool it (apparently he thought that the disliked aspect was if it was done unnecessarily). According to the Mālikite scholar Ibn Abī Zayd al-Qayrawānī the issue has to do with communal eating etiquette. If a person is eating alone then it is not disliked, but if they are eating in company, since it may gross people out, they should avoid it. This is also the opinion of al-Muhallab b. Abī Ṣufra, mentioned in his commentary on Ṣaḥīḥ al-Bukhārī and quoted by Ibn Ḥajar al-ʿAsqālānī.
The important Ḥanafī scholar Abū Yūsuf said it is permitted as long as it is not done so forcefully as to make a sound.
- Source for the Egyptian fatwa (Arabic PDF)