That little pin is on the switch that tells the starter circuit that the clutch is pulled in.
Normally, the electrical starter won't work if the transmission is not in neutral
unless the clutch is pulled in. Pulling in the clutch lever lets that switch pin move outward and bypasses the neutral lockout so the starter motor can operate even if the transmission is in gear. This can be real handy if the engine dies at a stop light.
With that little pin broken off and little or nothing protruding from the switch the electrical system will think the clutch is pulled in all of the time.
That will allow the starter motor to operate if the transmission is in gear and the clutch is not pulled in.
As long as you remember this and pull in the clutch everything will be just like the switch was working.
If you forget and leave the clutch lever untouched and hit the starter motor switch while the transmission is still in gear, your motorcycle could start and roar off down the road before you expect it to.