12V regulator for 100W LED
When you measured your LED drawing 6 A from a 30 V supply (if I understand right), that was 180 W. Your LED would not last long at that power. You do need a way to limit the current.

Best would be to find a 100 W current-regulated boost LED driver instead of a voltage-regulated boost regulator. Then you don't need any other components.

If you want to use a linear regulator, get a low-dropout regulator configured as a current and not as a voltage regulator. Then set the boost voltage as close to the LED voltage as the regulator dropout voltage will allow. If it's only one or two volts and 1 A, then only a couple Watts will be dissipated in the linear regulator, which is OK with an appropriate heatsink.

A word of caution about mounting a 100 W LED on a bike (I assume you mean bicycle): you really want to make sure that you have appropriate optics and diffusers in front of that LED so that the light comes from a large surface area (like car headlights) and not from a very small, 1 cm\$^2\$ point source. Otherwise you will badly blind anyone coming towards you, maybe even damaging their retinas, possibly causing an accident which may also involve you.