very much so, you don't mount your sensor in the light path of the led, as it will be cooked with a constant 10W of power, rather secure it very close to where the led die meets the heat sink,
as for how hot your led is getting, your led will have the relevant thermal resistance in oC per W, which for 10W is pretty easy, you then measure the heatsink at that point while running and add that temperature to what you expect for the led, e.g. a junction temp of 5 degrees per watt would be 50C rise, plus heat sink temp, or to better calculate also measure the ambient, this will give you a rough outline of the heat-sinks thermal resistance, so it might be 50C + 18C for the heat sink, + 22C for ambient,