Questions about my driver's license and turning 21 - having trouble finding this info elsewhere.

I turned 21 this past April, but my driver’s license says “under 21” and doesn’t expire until 2016.

I can find little information about getting it replaced for this reason, should I just follow the instructions for if your license is lost or stolen?

Furthermore, is it actually necessary to do so? I know my license is still valid but I’ve heard rumors that bars and liquor stores can turn down an “under 21” license even though my birth date is clearly more than 21 years ago, and I don’t want to deal with that.

I’m in PA. Thanks!