Does Riley have any other symptoms?
How long has he been cold?What is the temperature where Riley is?
Is he breathing?Has he been doing any vomiting or diarrhea?
Thanks for answering my questions.
In the absence of other symptoms, it's very likely that Riley simply has cold extremities.
Because he's such a young dog, I woudln't be worried about things that can cause compromised blood flow to the extremities such as heart problems or underlying organ disease.
If he starts showing other symptoms, such as lethargy, anorexia, vomiting or diarrhea, then you should have him seen by his vet, but at this point nothing that Riley has going on is setting off any warning signs for me.
I hope this helps.
It's possible that he's just lethargic because he's been vomiting all day. Since there's no possibility that he ate anything unusual and has a soft belly (which means he's not got bloat or some kind of GDV), and since it's only been one day, I don't think I'd be too worried just yet.
Of course, you know your dog better than anyone, so if you think he's ill enough to be worried about, then you should have him seen by an emergency vet tonight. Otherwise, have your regular vet take a peek at him in the morning.