This is VERY common thanks to the misconception that you aren't supposed to pull back on the left over foreskin of a circumcised baby.
It happened to my son b/c noone told me that you had to pull back and rinse for many months after healing to prevent adhesions.
Unfortunately, the only way they fix it is by sudden forcible retraction. The ped did it right there in the office. It hurt him somewhat, but there was no bleeding or anything. Then he told me to pull back on it every day and clean out any white cottage cheesy substance (called smegma. This is just bodily secretions and skin cells shedding as the foreskin begins to separate from the glans) because this is what causes it to adhere. Then to pull back and coat with vaseline frequently. My son is 17 months and has alot of leftover foreskin (many pediactricians leave a bit extra for them to grow into later in life) and I still pull it back and rinse it with water pretty frequently.
Good luck!