Many have came out of stammering, so can your son... He is small... so don't get worried... or don't show to him that you worry, otherwise he will be sad and worried by knowing that you worry for him... Instead do positive things... Love him, spend time with him, play with him.... The first step is .... When going to sleep, read poems together.... the one with tunes... with long melody... Then again poems with short melody... Then if he is willing to, try to read story book together (slowly) smoothly... Make sure that you understand his questions and answer him gently... Watch cartoons together.... Peppa Pig on Netflix is good.... Try to watch and read subtitles together when he gets old enough...