I assume they removed the polyp, even if it were benign. If Im not mistaken, a benign polyp does not require any special follow-ups and another colonoscopy would not be needed til you were 50.
I would visit the GI and let him know whats going on. Polyps take a long time to grow and even more to become cancer. Most of the timelines are 10 years, hence why colonoscopies are recommended at 50, because 60 is the age colon cancer becomes an issue.
I assume a barium xray is all that would be needed(if that) to see if theres any issues. I wouldnt worry too much about it being cancer. 2 years after a colonoscopy would be extremely unlikely for you to have developed cancer.
Normally after they find a polyp, they want to see you more often. I just went thru this where I was extremely constipated, took a laxative...nothing, suppository...nothing....enema...nothing. I feared the worst! But decided to give Activia Yogurt a try thinking I may need the probiotics, as a last ditch effort. Within 8 days I was back to normal and have remained good. But I didn't have any pain, and if I did I think I would have seen my GI doc. Because you had a polyp, and are having pain, I would see your GI. A single polyp can become large enough to make it difficult for you to have a bowel movement. While waiting to see him, eat Activia Yogurt, and you may return to normal before seeing him. But you should also ask him how often they want you to have a colonoscopy, normally it's every 3-5 years after they find a polyp. Take care.