I know you don't want to hear this, but yesterdays' and todays behavior with a cockerel is NOT an indicator about next week, or even tomorrow.
I think you did the right thing in thumping him back. If he had a chicken mama, she'd have cleaned his clock. In the chicken world, respect comes with distance. Closeness is not a sign of friendliness, but rather a sign of no fear, and disrespect. He will be expecting you to give into him, and can become much more aggressive to make it happen.
I am hoping you got it stopped now, it is a narrow window, and this forum is full of stories where the darling became the nightmare. The chick phase is past. You need to be very aware. It is not uncommon at all for a rooster to try it, and then be perfectly fine for several days, bidding his time. Waiting for a prime time to attack again.
Mrs K