Start over. Some times it takes a couple of tries. No big deal. Set your crank at TDC with the "T" mark. (1&4). Set your cam with the end notch lined up exactly to the deck of the head. Eyeball the bolt holes where they line up and put the cam chain on the sprocket. You will have to move the crank over a bit to get to the bolt holes one at a time. Once the sprocket is bolted up, recheck the timing of the cam to the crank. If it's off just a bit figure out which way the chain needs to go on the sprocket, unbolt it and inch-worm the chain in the right direction until it's timed just perfect. Keep an eye on your marks at all times as you can bump the crank or the cam, as you well know. And yes do remember to hold the tappets up in the valve cover before you bolt it down or you will bend your valves.