What is this mild pain I feel in my chest when I breathe in?

Age 20, male. It started yesterday when I noticed that I feel a pain in my chest when I breathe in. It’s nothing disruptive in my day to day life but it’s extremely annoying. I drink water constantly and admittedly I’ve been eating junk food. I think the junk food is the reason but today I’ve eaten healthier and the pain is still there. What would it be?