For a while now when I take my dog, he's almost 2 and is a heeler-pug mix, out to use the restroom ( I live in an apartment complex so everyone shares this courtyard) and I have to carefully watch my dog because when he picks up another dogs urine scent, he starts licking it up. I've tried many different ways to stop him but he still does it and it's gross cause he'll later on lick someone and that's unsanitary. Is it a dominant thing where he wan't to be the only scent any other dogs pick up? I really need this habit to go away.
Is it a dominant thing where he wan't to be the only scent any other dogs pick up?
No, it's more or less instinctive behavior. The dog doesn't want to get rid of the scent, he wants to literally get a better taste of it.
You can look it up if you're interested in this (dummies.com has a short version), but basically their mouth/nose are made in a special way that allows them to pick up some particles and sniff them several times. You might have seen your dog picking up a scent and then doing something which appeared to be chattering with their teeth (which they don't). They'll allow the air to circulate through their nose several times.
I really need this habit to go away.
Good luck with that. You might be able to do it with constant training (let the dog sniff, but distract once the licking starts), but it will be very hard and I'm not really sure it's really worth the trouble. It's gross, I probably agree, but at the same time it's something you can't avoid even if your dog isn't allowed to sniff outside (which would be bad for it).
Remember: The dog will clean itself, too, which also includes part of the dog body where gross things emerge. There's no way around that.
However, out of my mind I don't remember any disease you could get from your dog, which would be related to urine. Poo is a completely different thing, but at the same time your dog shouldn't touch that anyway (apart from the occasional sniff).
As a kind of alternative approach, when you know your dog licked up some scent, let it drink. Even if there are still small amounts of urine left, they'd be diluted significantly (which also happens through saliva).