Barking in the middle of the night?

My 4 month old male chin barked for the first time in the middle of the night. I had never heard him make the sound before so it really scared me, the high pitched squeaky and loud noises. He stopped when we turned on the light, and I sat and watched him for a while. I added more food to his bowl and he hasn't barked since but I am wondering if he is upset? Maybe I did something wrong? He should have been cool enough, plenty of water, clean bedding, the only thing i noticed is he managed to cover all of his food with hay, so I made more of it visible to him. Is this an issue? I am wondering what the barking means, since he has not made this sound and I have had him for nearly a month now. I am hoping he is not in pain or upset, but I really don't know what that was. Any comments would be appreciated! Thank you!

Sound you heard was most likely an alarm call, you chin probably heard something. Here is a short list of chins sounds that has the calling on it. Basically he probably heard something new to him or that he didn't like and was alerting everyone to it (in the wild that would be the herd, in the house he is alerting you). It could be anything from pipes rattling, heaters kicking in, a noise outside like a cat or dog or human, or noise from someone in the house if you live with anyone else, stuff like that. It's amazing how many noises we get use to in our day to day life that we don't even notice, but someone new picks up right away. By you getting up and turning on the light that signaled to him that you got the message, so no need to continue to bark. It can take some chins a month to fully get comfortable in their new home, some chins will cry right away at every new thing. Others are more cautious and don't want to make noise and give their location away so don't alert anyone to new things until they are comfortable.

Covering his food with hay (basically more food) is not going to make him cry, chins have a good sense of smell and are smart enough to remember the pellets are under the hay.