Responses
Basically Nick has been telling Owen that he's willing to wait for him until he's comfortable enough for them to bond or mark or fully release their pheromones with each other (since Owen is scared of his own pheromones, we know they haven't done it properly yet). The aunt is giving him a warning that Nick may say that he's willing to wait right now, but if Owen takes too long to open up and get to that stage, Nick might not actually wait that long and get together w another omega to get that dose of pheromones or whatever it is. That's why the aunt said "don't take too long".
At least this is what I understood!
I didn't understand the conversation with the Aunt. I mean Owen knows the nick wanna marry him and have kids and bond with him and they're soulmates so why the conversation with the Aunt startled him so much?