You may want to review the update notes, you must be level 58, have completed your level 48 pet quest, and completed nordrilund exposure quest from grandmother raven. If you have completed all of those, then visit your primary school teacher to see if they have the quest for you. If not then send a ticket to support.
the forest lord pet quest wont come i am in level 58 and i beat grissletusk
If you have finished Grizzlehiem and all but the very end of Wintertusk go she your teacher, she is the one that sends you to the fight in the first area of Wintertusk for your pet.