23 Month Boy: Understands words and sentences, but is not using many words: Should I worry?

My 23 month old boy Grant seems to understand a lot of words and sentences. I tell him to get his baby brother a toy; he does. I tell him to grab my ps4 controller, he does. It is evident he 'clearly' understands what I am saying however he really only says Mama, dada, doggy, car, and Uh Oh.Should I worry? My mother said don't worry because if he clearly understands, then he may just be a late bloomer.Opinions? via /r/Parenting http://ift.tt/2dVEaxk