Good luck with your chicken raising adventures, and I hope you find everything you need to know! Don't forget to take a look at BYC's very useful learning center! Glad to have you with us. I am not the one to help you with this, sorry. I don't have a rooster.
Basically you challenged him when you tapped his head. He already had the potential to be aggressive before you challenged him. There are lots of articles here on BYC on controlling roosters if they start attacking. Some roosters respond and others don't. This page has many threads on how to deal with aggressive roosters...
It's not your fault. What you did didn't cause his attitude to escalate. Total submission - wrapping him in a towel, forcing him to the ground and holding him there, carrying him around in a short handled fishing net all may modify his attitude, but deep inside he will remain untrustworthy. Understand that human aggressive roosters frequently produce sons with the same attitude. You might want to consider replacing him, and do not trust him around children.
the lady that I bought him from said he was non-aggressive. I held him today and he was calm I have hope. Btw the last roosters I had ended up in the pot.
Tapping on the head is what a rooster will do after a fight. They hold them down and peck at their head showing that the winner is the dominate one. I did the same to my rooster that attacked my leg twice, each time I pushed him to the ground and held him for a couple minutes then tapped him on the head to show him I was the dominate one. when I let him loose he got up and walked away. It took about 3 months before he tried it again. so I repeated the same thing and now He hasn't really attacked me but if I make a hen squawk, he'll come up and poke at my toe. Like saying "hey, fella" leave my hens alone. I move toward him and he goes away. Which normally it would be a challenge to him. But he hardly bothers me anymore.