The incident happened at 11.30am at a footpath near to Marmion Road when the young mum was assaulted and pulled the ground.
Police have confirmed that the mum sustained a minor facial injury in her fall as she tried to protect her son but that the little boy was unhurt.
They have issued a description of the man who is around six foot tall and was wearing a black hoodie and dark coloured jeans. He then made off without uttering a word.
Anyone with information is asked to contact police on 101.