Hi candangoek!
Yes, the only thing you have to do is report your tasks and ask for it once again, they points you get will be appears in your Quest Log:
Many players often collect boss points on lower level tasks and use them to kill the toughest task bosses in the upper levels.
After you collect 100 Tasks points you will be able to kill the bosses from low lever tasks, in case that you coudn't kill them before.
Edit: I found this page that have a very interesting explanation: Reddit_Boss Points.