Back home after a month at a crowded family house, baby is suddenly super cranky and sick.

Hey everyone, I’m feeling a bit overwhelmed today and could use some reassurance or advice.
We just got back home after staying at my parents house for a month. Over there, the house was packed with my siblings and his grandparents there was constant attention, love, and people around to hold him or play with him.
Now, we are finally back at our own place. My husband is back at work, so I’m completely alone with him during the day, i have a remote job too and the contrast is huge. The house is so quiet, and my baby has turned into a total velcro baby and is super cranky. To make things harder, he just came down with a runny nose and a little cough, so he’s physically miserable too.
Is this extreme fussiness just "environment shock" from missing all the family and noise, or is it mostly because he's under the weather? How long does it usually take for a baby to adjust back to a quiet home routine after being surrounded by a crowd?
Any tips on how to manage the congestion, keep him calm, and survive the day alone without losing my mind would be so appreciated. Thank you!