Question about adopted dog and 5-month-old cat

Hi! We adopted a dog a week ago and we have a 5-month-old kitten. The dog hasn't had any problems with the cat; in fact, every time they see each other they lick each other, greet each other, and are all very happy. The thing is, sometimes the cat bothers the dog, and the dog nudges him with his nose, and sometimes he puts his paws in the cat's mouth. I think it's not to bite him, just to play. Now, my question is, do you think the dog might get so annoyed that he attacks the cat? We're away from home for 6 or 7 hours a day, and sometimes we're afraid something might happen. What do you think we can do?