2nd flu shot sick

So my son got his second flu shot this past Tuesday and he got so sick. He currently is very congested, he has a very bad cough with phlegm that’s making him want to throw up. He’s hardly getting any sleep because of it. I have given him Tylenol for infants since he’s only 8 months old and he has the nasal spray but that’s all. His fevers come back during the night as well. I feel so bad I have no idea how to help feel better during bed time ): any advice please !