Puppies tend to throw up at times, but you really need to rule out that he may have eaten something he shouldn't have. I saw that you said he only ate once yesterday because you were at work. Puppies that age need to be fed 3-4 times a day. He is too young to have twice a day meals. Maybe you are giving him too much at one time- that will cause vomiting for sure. A pup that age should never be crated more than a few hours at a time. His total intake for the day should be spread out, and he should not be romping around right after eating- that will cause some vomiting also. A nice stroll right after eating will help him digest. Hope this helped.
If the vomiting continues, or he starts refusing his food, definitely a trip to the vet is warranted.