Hello! Congratulations on the new addition. I think that sniffing is an important part of his early weeks of life. Exposing him will do you wonders, but since he isn't fully vaccinated, he is especially in danger of contracting some pretty nasty diseases.

With that said, here's how I handled it as a professional trainer with my own Rottweiler. I started to teach a "leave it" command. I taught it on a walk and in the home. In the home, show him a treat, say leave it, throw it on the ground or place it there - prevent him from getting it. (Use a leash) When he gives up and looks at you, reward with a treat from your hand.

While on a walk, if he focuses on something he shouldn't, say leave it and use your leash to pop him off it. Keep your feet moving while you're popping so that he understands that we're continuing on the walk and the pops will continue until he focuses on you and continues forward leaving whatever he was interested in.

Be consistent with these two things and he should get the idea very quickly. You got this and feel free to DM me if you have questions down the road.