This "nozzle" may be part of your chain tensioning system. There is a small silver nub that goes into a hole on your bar. That nub is hooked up to a screw drive system. As you turn the chain adjuster, it moves that nub fore and aft. In turn that nub moves the bar fore and aft, changing the tension of the chain on the bar.

The bottom picture shows the Dolmar with the sprocket cover off. You can see the two bar studs that guide the bar. In between the two bar studs is a screw. This screw adjusts the position of the "nub" that sits right below and between the rear bar stud and the screw.

Masiman--

the nozzle/item in question is actually in the picture above the bottom picture. If you look, to the right of the bar, on the powerhead, you can see a small hole. It is on the front of the saw--not in the chain adjustment area.

I am not sure what that hole is. If I did not see inside the cover I would think it might be the chain tension adjuster (I have an older saw with the adjustment point there). But since I am pretty certain it is shown inside that cover between the studs I don't think it is the tensioner. Chain and bar oil is actually distributed through the bar, but you may already know this (at least on all the saws I have seen). The two holes on the north and south side of the studs, are where the oil goes into the bar. The upper hole is positioned over the oil outlet. The bottom hole, as previously mentioned, is used to move the bar fore and aft to change tension. With the symmetry it allows you to flip the bar, which you should do occasionally.

The Dolmar website had pretty good manuals, but I did not see that part clearly shown on the diagrams. There is a shop called Amicks that could easily answer your questions. They deal with alot of Dolmar saws and could likely quickly answer your question. They also apparently have excellent customer service (phone and in person).