The story probably dates from the late 80s to early 90s. I'm almost sure I read it in one of the pulp magazines while researching an article in the early '00s.
A physics professor, in a fit of exasperation with his teenaged son, tweaks things so that he ends up in a timeline where he never had a son. Except that his vanished life haunts his dreams, and in his new timeline he's not a good enough physicist to go back.
This sounds a lot like "Built upon the sands on time", a short story by Michael Flynn. Published in Analog July-August 2000 it is slightly later than your recollection, but so many details fit I think it is a plausible candidate.
A physics professor is married, and has a teenage son called Lenny who was "sullen, secretive. Seldom home even for meals", getting in trouble with the police, and so on. A teenager, basically. The professor builds a "chronon projector" which sends a perturbation (a "time quantum") back in time, and awakens in a strange house, with no wife or son. He has vague recollections from time to time of his alternate life and bitterly regrets his action.
One of the people he is telling the tale to asks why he cannot build another chronon projector and undo the effect, but he tells them that there is no chance that a random perturbation could have such a precise effect: "You may break the pack on a pool table with a well-aimed shot. you cannot bring the balls back together with another." So rather than being "a good enough physicist" to get back, as in the OP's question, it's really a case of natural law not permitting it.
