The man, who now lives in Skegness but cannot be named for legal reasons, was said to have been 'drifting apart' from his partner of 10 years, with whom he had two children, as well as a further child by his partner's previous relationship.
Boston Magistrates heard that on June 11 at what was then the family home in Friskney, the boy complained to his mother that his father had sworn at him and told him he could not have any tea, but his father then came in, denied saying that, swore again and slapped the boy on the arm, causing him pain.
Mitigating, Helen Coney said that at the time there had been difficulties in the marriage and relationships were strained.
She said things had now moved on after a period when he had no contact with his children but now had supervised contact and all safeguards were in place.
The magistrates imposed an 18 month conditional discharge and ordered him to pay £105 in court costs and charges.