J.B.
I have two thoughts that will I hope will ease your mind a bit! First, it's spring and allergens are in the air! My whole family is stuffy/runny right now as things are growing and blooming. Your baby might just be adjusting to the new spring "stuff" in the air.
Also, I remember my ped telling me that babies only breathe through their noses, so even when they have just a little congestion, it sounds much worse than it is. As adults, we breathe through both our mouths and noses, so we can "mask" our stuffy sounds a little better. Although your little one sounds stuffy, he probably isn't suffering as much as he may sound like he is, especially since you said he's still eating, etc.
If the eating changes, then I'd be concerned about dehydration, etc.