I'm mad at my so for gifting me fake flowers
Did you tell him you do not like fake flowers?
No I have not, I will tell him the truth
I know you do not like fake flowers, but you should be happy that the thought was there. This is why it is important to tell you significant other about what you like so things like this do not happen.
I'm still mad at him.
He tried to do something nice for you even if he fell short by your measure. Be appreciative of the effort he put in to make you happy and don't focus on the gift itself.