Chewing

Hi everyone! My son has recently started chewing/sucking on his fingers and also chewing on his shirts. He is a little anxious about switching full time into the preschool room from the toddler room. We've been gradually transitioning him already, but he knows his best friend is staying in the toddler room. He also sees his 1 year old sister chewing on things. Not sure if those things are triggering him to do it? This is a new behavior for him. Anyone else? Is this a phase or something I should be considered about?