Yep, if you are referring to the “arbor lug”.
It is there to stop the line from slipping around the spool when there is little line left. If it looks like a little steel mushroom, if you want - you can tie the line to it using the Uni-knot and pull down very tightly, which I would not do. I never tie the line directly to the lug.
If the lug has no mushroom cap, tie the line to the spool alongside the lug, again using the Uni-knot and pull the knot down tightly, with the knot hard up against the lug, which is what I do - with the first line wrap going over the lug.