Yes, you should be concerned, mostly about his not understanding. If you don't see some momentum developing around language over the next few months it would make sense to seek a Speech/Language evaluation.
hello Dr olsen i have a 23 month old son that used to say some word but since his brother was born he stop saying word my son was 1 year and 3month old and today some doctor came to the house to see him and she told me that he have pervasive developmental disorder nos i dont get because he do everything like a normal toddle only that he doesnt talk and when i call him he doesnt look at me in the eyes!!! i need help
See reply to your other note.