do we say to have a stitch? (avoir un point de côté) during a run for example (pain below the ribs).
Right, but a cramp would be "une crampe" in French, and would likely affect your leg (thigh, calf, ankle)...in my area, Northeast US, you would never say "I have a stitch". We use "cramp". After a mile run you might say, "Wow, I have a really bad cramp..."