It might be bruising, it might be gas (they blow you up during the procedure) and it might be an imbalance of gut bacteria caused by the prep. I’ve had two colonoscopies and discomfort afterwards both times.
I do think if they had damaged you it would be noticed immediately. Perforation of the bowel during colonoscopy is extremely rare (something like 1 in 10,000) and immediately obvious, with bleeding etc.