Next time, before its too late...

That's a good reason to put the crank 90 degrees away from TDC. Then NONE of the pistons are up at the top of their stroke, so spinning the cam can't do any damage.

Then when its all together, put the cams at their TDC timing position, where none of the valve are really open. Then spin the crank to put #1 at TDC so you can put on the timing belt.

If you've got real clearance issues, like non-stock cams or whatever; you can back your tappets off enough to close your valves when the cams are set at TDC. Then rotate your crank, put on the belt, then adjust valves.