Yes, you will need to get your son's W-2 and file his tax return if his gross income required him to file a tax return for 2020.
A single filer is required to file a tax return if the gross income is at least $12,400, please see Do I need to file a federal return this year? for additional details. Even if your son was not required to file a return this year, you might want to file one anyway to recover any 2020 federal tax withheld from his paychecks.