hi sounds like he has pulled or torn a muscle the best thing he van do is rest ice pack it a pack of frozen peas will done then he just keeps putting them back in the freezer don't eat them do it 3 times a day the slowly get back in to the swing of things but he must not rush it. keep him off any vigorous sex till then you will have to be on top but slowly. hope this helps. good luck
my boyfriend lifted some heavy tables last week and ever since he has a sharp pain on the right side of his stomach. he eats does not vomit or does not have a fever but it has been bothering him for a week and it is a sharp pain it only is relieved when he lays down on that side.