Should A Pop Sound From Superior Midline Calf Be Of Medical Concern?

my 50 year old neighbor stopped,after driving for an hour, to help push an old lady's car out of an interection. She put it in neutral and it rolled back resulting in him grossly overexerting. He felt a "pop" (similar to a small thump) in his superior midline calf, 1 inch below the posterior knee. He can flex his foot. However, he has pain on weightbearing. No swelling, bruising or obvious difference from his left calf. Thanks,....