Common cold and flu vaccination.

My son zayaan have nose infection from last one month. In this month he has taken augmentin es syrup  and allercet m tablet for 5 days twice for throat infection .But this time he was free from nose problem. Now a he has some runing nose, no fever. We have given him flu vaccine on 26.05.25.on 27.05  in afternoon he get sparyed nasal saline spary while taking bath and he get fainted for a while. We get afraid looking to him like this for fist time in 13 years. So taken him to bed and laid down. Given some food biscuit and apple as he had not taken any food from morning. After taking some food and water he felt good and we allowed him to sleep. After some  Rest he taken food properly and taking rest. But we are afraid why this happen to him. Can I reuqest to please suggest me what is this and what care we have to take to make him healthy and avoid such situation. Also in running nose what we can do at home. Or what is best medicine