Worried after 1year old swallowed penny?

My 1 year old swallowed a penny and it ped through his system. We didn't know he had swallowed one until we found it in his diaper(yes it was a scary moment). when it came out he had hard dry stool like little pebbles. Its been two days since the penny ped and hes still having hard dry stools. We've been trying to loosen him up but so far its not working. Should I be worried? could this be related to the penny swallowing? aside that he seems ok