It is most probably a coincidence.
You should know that the Flu Jab consists of the current Virus that is on the go but they are dead. The cannot cause you to have the flu. In simplest terms all they do is make your body produce the antibodies to fight off the flu should you get it.
They are not live virus cells - it is common though to have some side effects. Don't let this experience put you off. I have my Flu jab every year and suffer quietly for a few days. Rather have that than spend days or weeks in hospital should I get hit with the flu.