I built a high power LED light a few years ago and when doing research on LED thermal management found it is common for operating temps to reach +120F. This is hot enough that you wouldn't be able to touch it for more than a few seconds. If the light feels hot to the touch, it probably just means the heatsink is doing its job well. If the LED became detached from the heatsink it would burn out in a matter of seconds on full power and the light wouldn't feel hot.

A heatsinks ability to dissipate heat depends on how much air is flowing over it and the ambient air temp. If the light is powered up indoors and sitting on a table it will get much hotter than when riding with it. My light sometimes kicks into thermal protection mode (turns off) when climbing hills on hot summer nights or waiting at stoplights. I like to use this "feature" as motivation to ride faster up the hills.